JP2004182858A - Alkaline saponification method of cellulose acylate film, surface-saponified cellulose acylate film and optical film using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline saponification method with which a cellulose acylate film is saponified stably and evenly across the entire surface, a surface-saponified acylate film suitable for an optical compensation film for use in a large liquid crystal display with no display defects and an alkaline saponified film for use in an optical compensation film having a good adhesion to a transparent support and an alignment layer. <P>SOLUTION: The alkaline saponification method of a cellulose acylate film, more specifically a method with which the alkaline solution is coated only on one side of the film and the side is selectively saponified comprises alkaline-saponifying the cellulose acylate film using the alkaline solution containing at least an alkaline agent, water, an organic solvent, a compatibilizer and a surfactant. The cellulose acylate film is obtained by the alkaline saponification method. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

また、有機溶媒、とりわけ上記有機性と溶解性の各範囲の有機溶媒、を後述する相溶化剤及び界面活性剤と組み合わせて用いると高い鹸化速度が維持されて、かつ全面に亘る鹸化度の均一性が向上する。
【００３７】
好ましい特性値を有する有機溶媒は、例えば、有機合成化学協会編、「新版溶剤ポケットブック」（（株）オーム社、１９９４年刊）等に記載のものが挙げられている。（また、有機溶媒の無機性／有機性値（Ｉ／Ｏ値）については、例えば、田中善生著有機概念図）三共出版社１９８３年刊、１〜３１頁に解説されている）。
【００３８】
具体的には、一価脂肪族アルコール類（例、メタノール、エタノール、プロパノール、ブタノール、ペンタノール、ヘキサノール等）、脂環式アルカノール（例、シクロヘキサノール、メチルシクロヘキサノール、メトキシシクロヘキサノール、シクロヘキシルメタノール、シクロヘキシルエタノール、シクロヘキシルプロパノール等）、フェニルアルカノール（例、べンジルアルコール、フェニルエタノール、フェニルプロパノール、フェノキシエタノール、メトキシベンジルアルコール、ベンジルオキシエタノール等）、複素環式アルカノール類（フルフリルアルコール、テトラヒドロフルフリルアルコール等）、グリコール化合物のモノエーテル類（メチルセルソルブ、エチルセルソルブ、プロピルセルソルブ、メトキシメトキシエタノール、ブチルセルソルブ、ヘキシルセルソルブ、メチルカルビトール、エチルカルビトール、プロピルカルビトール、ブチルカルビトール、メトキシトリグリコール、エトキシトリグリコール、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノプロピルエーテル等）ケトン類（例、アセトン、メチルエチルケトン、メチルイソブチルケトン等）、、アミド類（例、Ｎ，Ｎ−ジメチルホルムアミド、ジメチルホルムアミド、Ｎ―メチルー２−ピロリドン、１，３ジメチルイミダゾリジノン等）、スルホキシド類（例、ジメチルスルホキシド）およびエーテル類（例、テトラヒドロフラン、ピラン、ジオキサン、トリオキサン、ジメチルセルソルブ、ジエチルセルソルブ、ジプロピルセルソルブ、メチルエチルセルソルブ、ジメチルカルビトール、ジメチルカルビトール、メチルエチルカルビトール等）等が挙げられる。用いる有機溶媒は、単独若しくは２種以上を混合して用いてもよい。
【００３９】
有機溶媒を単独或いは２種以上を混合する場合の少なくとも一種の有機溶媒は、水への溶解性が大きなものが好ましい。有機溶媒の水の溶解度は、５０質量％以上が好ましく、水と自由に混合するものがより好ましい。アルカリ剤、鹸化処理で副生する脂肪酸の塩、空気中の二酸化炭素を吸収して生じた炭酸の塩等への溶解性が充分なアルカリ溶液を調製できる。
有機溶媒の溶媒中の使用割合は、溶媒の種類、水との混和性（溶解性）、反応温度および反応時間に応じて決定する。短い時間で鹸化反応を完了するためには、高い濃度に溶液を調製することが好ましい。ただし、溶媒濃度が高すぎるとアシレートフィルム中の成分（可塑剤など）が抽出されたり、フィルムの過度の膨潤が起こる場合があり、適切に選択する必要がある。
水と有機溶媒の混合比は、３／９７〜８５／１５質量比が好ましい。より好ましくは５／９５〜６０／４０質量比であり、更に好ましくは１５／８５〜４０／６０質量比である。この範囲において、アシレートフィルムの光学特性を損なうことなく容易にフィルム全面が均一に鹸化処理される。
【００４０】
本発明に用いるアルカリ溶液が含有する有機溶媒には、上記した本発明の目的であるヘイズを低減させ、鹸化度の均一性や安定性を高める作用を持つ有機溶媒のほかに、共存させることによって発明の効果を増大させることができる後述するアルカリ溶液への界面活性剤及び相溶化剤や消泡剤の溶解助剤の作用を有する有機溶媒も含まれる。この作用を有する有機溶媒は、上記した好ましいＩ／Ｏ値を有する有機溶媒とは異なる有機溶媒であってもよい。溶解助剤作用を有する好ましい有機溶媒は、例えば、Ｎ−フェニルエタノールアミンおよびＮ−フェニルジエタノールアミン、フッ化アルコール（例えば、Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｋＯＨ（ｎは３〜８の整数、ｋは１又は２の整数）、１，２，２，３，３−ヘプタフロロプロパノール、ヘキサフロロブタンジオール、パーフロロシクロヘキサノール等）等を挙げることができる。溶解助剤の目的で用いられる有機溶媒の含有量は使用液の総重量に対して０．１〜５％が好ましい。
【００４１】
本発明に用いるアルカリ溶液は、界面活性剤を含有する。界面活性剤を添加することによって表面張力を下げて塗布を容易にしたり、塗膜の均一性を上げてハジキ故障を防止し、かつ有機溶媒が存在すると起こり易いヘイズを抑止し、さらに鹸化反応が均一に進行する。その効果は、後述する相溶化剤の共存によって特に顕著となる。用いられる界面活性剤には特に制限はなく、アニオン界面活性剤、カチオン界面活性剤、両性界面活性剤、ノニオン界面活性剤、フッ素系界面活性剤等のいずれであってもよい。
【００４２】
以下、本発明に使用しうる界面活性剤について順次説明する。
（アニオン界面活性剤）
アニオン界面活性剤としては、例えば、脂肪酸塩類、アビエチン酸塩類、ヒドロキシアルカンスルホン酸塩類、アルカンスルホン酸塩類、ジアルキルスルホ琥珀酸エステル塩類、αオレフィンスルホン酸塩類、直鎖アルキルベンゼンスルホン酸塩類、分岐鎖アルキルベンゼンスルホン酸塩類、アルキルナフタレンスルホン酸塩類、アルキルフェノキシポリオキシエチレンプロピルスルホン酸塩類、ポリオキシエチレンアルキルスルホフェニルエーテル塩類、Ｎ−メチル−Ｎ−オレイルタウリンナトリウム塩、Ｎ−アルキルスルホ琥珀酸モノアミド二ナトリウム塩、石油スルホン酸塩類、硫酸化牛脂油、脂肪酸アルキルエステルの硫酸エステル塩類、アルキル硫酸エステル塩類、ポリオキシエチレンアルキルエーテル硫酸エステル塩類、脂肪酸モノグリセリド硫酸エステル塩類、ポリオキシエチレンアルキルフェニルエーテル硫酸エステル塩類、ポリオキシエチレンスチリルフェニルエーテル硫酸エステル塩類、アルキルリン酸エステル塩類、ポリオキシエチレンアルキルエーテルリン酸エステル塩類、ポリオキシエチレンアルキルフェニルエーテルリン酸エステル塩類、スチレン／無水マレイン酸共重合物の部分鹸化物類、オレフィン／無水マレイン酸共重合物の部分鹸化物類、ナフタレンスルホン酸塩ホルマリン縮合物類等が好適に挙げられる。
【００４３】
（カチオン界面活性剤）
カチオン界面活性剤としては、例えば、アルキルアミン塩類、テトラブチルアンモニウムブロミド等の第四級アンモニウム塩類、ポリオキシエチレンアルキルアミン塩類、ポリエチレンポリアミン誘導体等が挙げられる。
【００４４】
（両性界面活性剤）
両性界面活性剤としては、例えば、カルボキシベタイン類、アルキルアミノカルボン酸類、スルホベタイン類、アミノ硫酸エステル類、イミダゾリン類等が挙げられる。
【００４５】
（ノニオン性界面活性剤）
ノニオン性界面活性剤としては、例えば、ポリオキシエチレンアルキルエーテル類、ポリオキシエチレンアルキルフェニルエーテル類、ポリオキシエチレンポリスチリルフェニルエーテル類、ポリオキシエチレンポリオキシプロピレンアルキルエーテル類、グリセリン脂肪酸部分エステル類、ソルビタン脂肪酸部分エステル類、ペンタエリスリトール脂肪酸部分エステル類、プロピレングリコールモノ脂肪酸エステル類、しょ糖脂肪酸部分エステル類、ポリオキシエチレンソルビタン脂肪酸部分エステル類、ポリオキシエチレンソルビトール脂肪酸部分エステル類、ポリエチレングリコール脂肪酸エステル類、ポリグリセリン脂肪酸部分エステル類、ポリオキシエチレン化ひまし油類、ポリオキシエチレングリセリン脂肪酸部分エステル類、脂肪酸ジエタノールアミド類、Ｎ，Ｎ−ビス−２−ヒドロキシアルキルアミン類、ポリオキシエチレンアルキルアミン、トリエタノールアミン脂肪酸エステル、トリアルキルアミンオキシド等が挙げられる。
【００４６】
これらの具体例を示すと、例えば、ポリエチレングリコール、ポリオキシエチレンラウリルエーテル、ポリオキシエチレンノニルエーテル、ポリオキシエチレンセチルエーテル、ポリオキシエチレンステアリルエーテル、ポリオキシエチレンオレイルエーテル、ポリオキシエチレンベヘニルエーテル、ポリオキシエチレンポリオキシプロピレンセチルエーテル、ポリオキシエチレンポリオキシプロピレンベヘニルエーテル、ポリオキシエチレンフェニルエーテル、ポリオキシエチレンオクチルフェニルエーテル、ポリオキシエチレンステアリルアミン、ポリオキシエチレンオレイルアミン、ポリオキシエチレンステアリン酸アミド、ポリオキシエチレンオレイン酸アミド、ポリオキシエチレンひまし油、ポリオキシエチレンエチレンアビエチルエーテル、ポリオキシエチレンノニンエーテル、ポリオキシエチレンモノラウレート、ポリオキシエチレンモノステアレート、ポリオキシエチレングリセリルモノオレート、ポリオキシエチレングリセリルモノステアレート、ポリオキシエチレンプロピレングリコールモノステアレート、オキシエチレンオキシプロピレンブロックポリマー、ジスチレン化フェノールポリエチレンオキシド付加物、トリベンジルフェノールポリエチレンオキシド付加物、オクチルフェノールポリオキシエチレンポリオキシプロピレン付加物、グリセロールモノステアレート、ソルビタンモノラウレート、ポリオキシエチレンソルビタンモノラウレート等が挙げられる。これらのノニオン性界面活性剤の重量平均分子量は、３００〜５０，０００が好ましく、５００〜５，０００が特に好ましい。
【００４７】
本発明において、前記ノニオン性界面活性剤の中でも、下記一般式（１）で表される化合物が好ましい。
一般式（１）： Ｒ^１−Ｏ（ＣＨ_２ＣＨＲ^２Ｏ）_ｌ−（ＣＨ_２ＣＨＲ^３Ｏ）_ｍ−（ＣＨ_２ＣＨＲ^４Ｏ）_ｎ−Ｒ^５
一般式（１）中、Ｒ^１〜Ｒ^５は、それぞれ、水素原子、炭素数１〜１８のアルキル基、アルケニル基、アルキニル基、アリール基、カルボニル基、カルボキシレート基、スルホニル基、スルホネート基を表す。
前記アルキル基の具体例としては、メチル基、エチル基、ヘキシル基等が挙げられ、前記アルケニル基の具体例としては、ビニル基、プロペニル基等が挙げられ、前記アルキニル基の具体例としては、アセチル基、プロピニル基等が挙げられ、前記アリール基の具体例としては、フェニル基、４−ヒドロキシフェニル基等が挙げられる。
ｌ，ｍ，ｎは０以上の整数を表す。但し、ｌ，ｍ，ｎの総てが０であることはない。
一般式（１）で表される化合物の具体例としては、ポリエチレングリコール、ポリプロピレングリコール等のホモポリマー、エチレングリコール、プロピレングリコールの共重合体等が挙げられる。前記共重合体の比率は、１０／９０〜９０／１０がアルカリ溶液への溶解性の点から好ましい。また、共重合体の中でもグラフトポリマー、ブロックポリマーが、アルカリ溶液に対する溶解性とアルカリ鹸化処理の容易性の点から好ましい。
【００４８】
（フッ素系界面活性剤）
フッ素系界面活性剤は、分子内にパーフルオロアルキル基を含有する界面活性剤を指す。このようなフッ素系界面活性剤としては、例えば、パーフルオロアルキルカルボン酸塩、パーフルオロアルキルスルホン酸塩、パーフルオロアルキルリン酸エステル等のアニオン型、パーフルオロアルキルベタイン等の両性型、パーフルオロアルキルトリメチルアンモニウム塩等のカチオン型、パーフルオロアルキルアミンオキサイド、パーフルオロアルキルエチレンオキシド付加物、パーフルオロアルキル基及び親水性基含有オリゴマー、パーフルオロアルキル基及び親油性基含有オリゴマー、パーフルオロアルキル基、親水性基及び親油性基含有オリゴマー、パーフルオロアルキル基及び親油性基含有ウレタン等の非イオン型が挙げられる。
以上の界面活性剤のうち、「ポリオキシエチレン」とあるものは、ポリオキシメチレン、ポリオキシプロピレン、ポリオキシブチレン等のポリオキシアルキレンに読み替えることもでき、それらもまた前記界面活性剤に包含される。前記界面活性剤は、一種単独で使用してもよいし、併用により効果を損なわない限りにおいては、２種以上を併用してもよい。
【００４９】
以上の界面活性剤の中でも、本発明においては、カチオン性界面活性剤としての前記４級アンモニウム塩類、ノニオン性界面活性剤としての前記各種のポリエチレングリコール誘導体類、前記各種のポリエチレンオキサイド付加物類等のポリエチレンオキサイド誘導体類、両性界面活性剤としてのベタイン型化合物類が好ましい。
アルカリ溶液には、ノニオン活性剤とアニオン活性剤又はノニオン活性剤とカチオン活性剤を共存させて用いることも本発明の効果が高められて好ましい。
【００５０】
これらの界面活性剤のアルカリ溶液に対する添加量は、好ましくは、０．００１〜２０質量％であり、より好ましくは、０．０１〜１０質量％であり、特に好ましくは、０．０３〜３質量％である。添加量が、０．００１質量％より少ない場合には、界面活性剤の添加効果が得難く、２０質量％よりも多い場合には、鹸化性が低下する傾向がある
【００５１】
本発明に用いるアルカリ溶液は、相溶化剤を含有する。本発明において相溶化剤とは、温度２５℃において、相溶化剤１００ｇに対して水の溶解度が３０ｇ以上となる親水性化合物である。好ましくは、水の溶解度が５０ｇ／１００ｇであり、より好ましくは１００ｇ／１００ｇである。また、本発明における相溶化剤が液状化合物の場合は、沸点が１００℃以上であることが好ましく、より好ましくは１２０℃以上である。
本発明に係るアルカリ処理浴の装置において、相溶化剤は、壁面に付着したアルカリ液の乾燥を防止し固着を抑制し溶液を安定に保持することが出来る。又、フィルム表面にアルカリ液を塗布して一定時間保持したのち鹸化停止処置をするまでの間に塗布された薄膜が乾燥し固形物の析出が生じ、水洗工程での固形物の洗い出しが困難になることを抑止する。更には、溶媒となる水と有機溶媒の相分離を防止する。とりわけ、界面活性剤と有機溶媒と上記規定の相溶化剤との共存によって、処理されたフィルムは、ヘイズが減少し、かつ長尺の連続鹸化処理の場合であっても安定して全面均一な鹸化度が得られる。
【００５２】
本発明に用いる相溶化剤は、上記の条件を満たす材料であれば、いずれの材料であっても相溶化剤として用いることができる。好ましい相溶化剤としては、ポリオール化合物、糖類を始めとするヒドロキシ基及び／又はアミド基を有する繰り返し単位を含む水溶性重合体が挙げられる。
ポリオール化合物としては、低分子化合物、オリゴマー化合物、高分子化合物の何れでもよい。例えば、脂肪族ポリオール類としては、炭素数２〜８のアルカンジオール（例えばエチレングリコール、プロピレングリコール、ブタンジオール、ペンタンジオール、ヘキサンジオール、グリセリンモノメチルエーテル、グリセリンモノエチルエーテル、シクロヘキサンジオール、シクロヘキサンジメタノール、ジエチレングリコール、ジプロピレングリコール等）、ヒドロキシ基を３個以上含有する炭素数３〜１８のアルカン類（例えば、グリセリン、トリメチロールエタン、トリメチロールプロパン、トリメチロールブタン、ヘキサントリオール、ペンタエリスリトール、ジグリセリン、ジペンタエリスリトール、イノシットール等）、ポリアルキレンオキシポリオール類としては、上記のような同じアルキレンジオール同士が結合していても異なるアルキレンジオールが互いに結合していてもよいが、同じアルキレンジオール同士が結合したポリアルキレンポリオールがより好ましい。いずれの場合もの結合数は３〜１００が好ましい。より好ましくは３〜５０である。具体的にはポリエチレングリコール、ポリプロピレングリコール、ポリ（オキシエチレンーオキシプロピレン）等が挙げられる。
【００５３】
糖類としては、例えば、高分子学会高分子実験学編集委員会編「天然高分子」第二章（共立出版（株）、１９８４年刊）、小田良平等編「近代工業化学２２、天然物工業化学ＩＩ」（（株）朝倉書店、１９６７年刊）等に記載の水溶性化合物が挙げられる。遊離のアルデヒド基やケトン基を持たない還元性を示さない糖類が好ましい。グルコース、スクロース、還元基同士の結合したトレハロース型少糖類、糖類の還元基と非糖類が結合した配糖体および糖類に水素添加して還元した糖アルコールに分類され、何れも本発明に好適に用いられる。トレハロース型少糖類には、サッカロースやトレハロースがあり、配糖体としては、アルキル配糖体、フェノール配糖体、カラシ油配糖体などが挙げられる。また糖アルコールとしてはＤ，Ｌ−アラビット、リビット、キシリット、Ｄ，Ｌ−ソルビット、Ｄ，Ｌ−マンニット、Ｄ，Ｌ−イジット、Ｄ，Ｌ−タリット、ズリシットおよびアロズルシットなどが挙げられる。更に二糖類の水素添加で得られるマルチビットおよびオリゴ糖の水素添加で得られる還元体（還元水あめ）も好適に用いられる。これらの中で本発明に好ましい非還元糖は糖アルコールとサッカロースであり、特にＤ−ソルビット、サッカロース、還元水あめが適度なｐＨ領域に緩衝作用があることと、低価格であることで好ましい。これらの非還元糖は、単独もしくは二種以上を組み合わせて使用出来る。
【００５４】
ヒドロキシ基及び／又はアミド基含有の繰り返し単位を含有する水溶性重合体としては、天然ガム類（例えば、アラビアガム、グアーガム、トラガンドガム等）、ポリビニルアルコール、ポリビニルピロリドン、ジヒドキシプロピルアクリレート重合体、セルロース類やキトサン類のエチレンオキサイド或いはプロピレンオキサイドとのエポキシ化合物との付加反応体、アルキレンポリオール、ポリアルキレンオキシポリオール、糖アルコール等が挙げられる。
中でも好ましくは、アルキレンポリオール、ポリアルキレンオキシポリオール及び糖アルコールが挙げられる。具体的には、エチレングリコール、プロピレングリコール、ブチレングリコール、ジエチレングリコール、ジ（ｎ−プロピレングリコール）、ジ（ｉ−プロピレングリコール）、ポリエチレングリコール（結合数３〜２０）、ポリプロピレングリコール（結合数３〜１０）、さらには、グリセリン、ジグリセリンが挙げられる。
【００５５】
これらの相溶化剤の含有量は、アルカリ溶液中の０．５〜３５質量％が好ましく、１〜２５質量％がより好ましい。
【００５６】
更に、本発明におけるアルカリ溶液には消泡剤を含有させることが好ましい。この添加剤は、アルカリ溶液中に、好ましくは０．００１〜５質量％、特に好ましくは０．００５〜３重量％の濃度で含有させることができる。
この範囲において、フィルム表面への微小な気泡の付着も無くなり、アルカリ処理による鹸化がムラ無く均一に進行する。
【００５７】
消泡剤としては、ヒマシ油、亜麻仁油等の油脂系、ステアリン酸、オレイン酸等の脂肪酸系、天然ワックス等の脂肪酸エステル系、ポリオキシアルキレンモノハイドリックアルコール等のアルコール系、ジ−ｔ−アミルフェノキシエタノール、ヘプチルセロソルブ、ノニルセロソルブ、３−ヘプチルカルビトール等のエーテル系、トリブチルフォスフェート、トリス（ブトキシエチル）フォスフェート等の燐酸エステル系、ジアミルアミン等のアミン系、ポリアルキレンアミド、アシレートポリアミド等のアミド系、ステアリン酸アルミニウム、ステアリン酸カルシウム、オレイン酸カリウム、羊毛オレイン酸のカルシウム塩等の金属石鹸系、ラウリル硫酸エステルナトリウム等の硫酸エステル系、ジメチルポリシロキサン、メチルフェニルポリシロキサン、メチル水素ポリシロキサン、フロロポリシロキサン、ジメチルポリシロキサンとポリアルキレンオキサイドとの共重合体等のシリコーンオイル、及びその溶液型、エマルジョン型、ペースト型シリコーンオイル等のシリコーン系の消泡剤が挙げられる。
【００５８】
本発明に用いるアルカリ溶液には、更に、防黴剤及び／又は防菌剤を含有させることが好ましい。本発明において使用される防黴剤及び防菌剤は、アルカリ鹸化に悪影響を及ぼさないものであれば何でもよいが、具体的にはチアゾリルベンズイミダゾール系化合物、イソチアゾロン系化合物、クロロフェノール系化合物、ブロモフェノール系化合物、チオシアン酸やイソチアン酸系化合物、酸アジド系化合物、ダイアジンやトリアジン系化合物、チオ尿素系化合物、アルキルグアニジン化合物、４級アンモニウム塩、有機スズや有機亜鉛化合物、シクロヘキシルフェノール系化合物、イミダゾール及びベンズイミダゾール系化合物、スルファミド系化合物、塩素化イソシアヌル酸ナトリウムなどの活性ハロゲン系化合物、キレート剤、亜硫酸化合物、ペニシリンに代表される抗生物質など種々の防バクテリア剤や防黴剤などがある。その他Ｌ．Ｅ．Ｗｅｓｔ，”Ｗａｔｅｒ Ｑｕａｌｉｔｙ Ｃｒｉｔｅｒｉａ”Ｐｈｏｔ．Ｓｃｉ．ａｎｄ Ｅｎｇ．，Ｖｏｌ９ Ｎｏ．６（１９６５）記載の殺菌剤、特開昭５７−８５４２号、同５８−１０５１４５号、同５９−１２６５３３号、同５５−１１１９４２号、同５７−１５７２４４号公報記載の各種防黴剤、「防菌防黴の化学」堀口博著・三共出版（昭５７）、「防菌防黴技術ハンドブック」日本防菌防黴学会・技報堂（昭６１）に記載されているような化学物などを用いることができ、以下に具体例を示すが、これらに限定されるものではない。
上記した防黴剤及び／又は防菌剤の添加量は、アルカリ溶液中に０．０１〜５０ｇ／Ｌであることが好ましく、より好ましくは０．０５〜２０ｇ／Ｌである。
【００５９】
尚、本発明に用いるアルカリ溶液には、他の添加剤を併用しても良い。例えば、アルカリ液安定化剤（酸化防止剤等）等が挙げられる。尚、本発明においてアルカリ溶液の添加剤は、これらに限定されるものではない。
【００６０】
又、アルカリ溶液に用いる水としては、日本国水道法（昭和３２年法律第１７７号）及びそれに基づく水質基準に関する省令（昭和５３年８月３１日厚生省令第５６号）、同国温泉法（昭和２３年７月１０日法律第１２５号及びその別表）、及び、ＷＨＯ規定水道水基準によって規定される水中の混入の状態に於ける各元素やミネラル等への影響、等に基づくものが好ましい。更に、本発明の効果の達成をより確実にするために、カルシウム濃度が、炭酸カルシウムとしての濃度として、０．００１〜２００ｍｇ／Ｌであるのが好ましく、０．０１〜１５０ｍｇ／Ｌであるのが更に好ましく、０．０５〜１０ｍｇ／Ｌであるのが特に好ましい。この範囲で、溶液中の不溶解物の生成が抑えられる。
【００６１】
上記の組成物からなるアルカリ溶液は、その溶液の表面張力が４５ｍＮ／ｍ以下（温度２５℃）であり，且つ粘度が０．８〜２０ｍＰａ・ｓ（温度２５℃）の範囲であることが好ましい。好ましくは、表面張力が２０〜４０ｍＮ／ｍ（温度２５℃）であり，且つ粘度が１〜１５ｍＰａ・ｓ（温度２５℃）である。この範囲において、フィルム表面への濡れ性、フィルム表面に塗布した溶液の保持性、鹸化処理後のフィルム表面からのアルカリ液の除去が充分に行われる。
【００６２】
［アルカリ鹸化方法］
上記のアルカリ溶液を用いたセルロースアシレートフィルムの表面処理方法は従来公知のいずれの方法でもよく、浸漬方法、吹き付け方法、塗布方法等が挙げられる。
特に、フィルムの片面のみをムラ無く均一に鹸化処理する場合は、塗布方式が好ましい。塗布の方法としては、後に述べるように従来公知の塗布方法を用いることができる。
鹸化処理は、処理するフィルムの変形、処理液の変質等が生じない温度１２０℃を越えない範囲の処理温度で行うことが好ましい。更に温度１０℃以上であり１００℃以下の範囲が好ましい。特に、温度２０〜８０度が好ましい。
更に、塗布方式で処理する場合には、セルロースアシレートフイルムをその表面が少なくとも１０℃以上の温度でアルカリ溶液で鹸化処理する工程、セルロースアシレートフイルムの温度を少なくとも１０℃以上に維持する工程、そして、アルカリ溶液をセルロースアシレートフイルムから洗い落とす工程によりアルカリ鹸化処理を実施することが好ましい。
セルロースアシレートフイルムをその表面が所定の温度でアルカリ溶液で鹸化処理には、塗布する前に予め所定の温度に調整する工程、アルカリ液を予め所定の温度に調整しておく工程、或いはこれらを組み合わせた工程等が挙げられる。塗布する前に予め所定の温度に調整する工程と組み合わせることが好ましい。
【００６３】
好ましくは、セルロースアシレートフイルムを予め２０度以上に温度調整する工程では、所定温度風の衝突、伝熱ロールによる接触伝熱、マイクロ波による誘導加熱、あるいは赤外線ヒーターによる輻射熱加熱が好ましく利用できる。特に伝熱ロールによる接触伝熱は、熱伝達効率が高く小さな設置面積で行える点、搬送開始時のフイルム温度の立上りが速い点で好ましい。一般の２重ジャケットロールや電磁誘導ロール（トクデン社製）が利用できる。
【００６４】
セルロースアシレートフイルムをアルカリ溶液で鹸化処理する工程は、塗布量の変動をフイルムの幅方向および長さ方向に対して３０％未満に抑制することが好ましい。
塗布方式としては、例えば、ダイコーター（エクストルージョンコーター、スライドコーター）、ロールコーター（順転ロールコーター、逆転ロールコーター、グラビアコーター）、ロッド（細い金属線を巻いたロッド）コーター、ブレードコーターなどが好ましく利用できる。塗布方式に関しては、各種文献（例えば、Ｍｏｄｅｒｎ Ｃｏａｔｉｎｇ ａｎｄ Ｄｒｙｉｎｇ Ｔｅｃｈｎｏｌｏｇｙ， Ｅｄｗａｒｄ Ｃｏｈｅｎ ａｎｄ Ｅｄｇａｒ Ｂ． Ｇｕｔｏｆｆ， Ｅｄｉｔｓ．， ＶＣＨ Ｐｕｂｌｉｓｈｅｒｓ， Ｉｎｃ， １９９２ ）に記載されている。アルカリ溶液の塗布量は、その後、水洗除去するため廃液処理を考慮して、極力抑制することが望ましい。少ない塗布量でも安定に操作できるロッドコーター、ダイコーター、グラビアコーターおよびブレードコーターが特に好ましい。
また、連続塗布方式を採用することも好ましい。
【００６５】
鹸化反応に必要なアルカリ塗布量は、セルロースアシレートフイルムの単位面積当りの鹸化反応サイト数に配向膜との密着を発現させるために必要な鹸化深さを乗じた総鹸化サイト数（＝理論アルカリ塗布量）が目安となる。鹸化反応の進行にともなってアルカリ剤が消費され反応速度が低下するため、実際には上述の理論アルカリ塗布量の数倍を塗布することが好ましい。具体的には、理論アルカリ塗布量の２〜２０倍であることが好ましく、２〜５倍であることがさらに好ましい。
アルカリ溶液の温度は、反応温度（＝フイルムの温度）に等しいことが望ましい。
【００６６】
アルカリ溶液を塗布した後、鹸化反応が終了するまで、セルロースアシレートフイルムの温度を少なくとも１０℃以上に保つ。好ましくは１５℃以上である。
加熱手段は、セルロースアシレートフイルムの片面がアルカリ溶液により濡れている状態であることを考慮して選択する。例えば塗布面の反対側の面への熱風の吹き付け、加熱ロールによる接触伝熱、マイクロ波による誘導加熱、あるいは、赤外線ヒーターによる輻射熱加熱が好ましく利用できる。赤外線ヒーターは、非接触、かつ空気の流れを伴わずに加熱できるため、アルカリ溶液塗布面への影響を最小にできるため好ましい。赤外線ヒーターは、電気式、ガス式、オイル式あるいはスチーム式の遠赤外セラミックヒーターが利用できる。熱媒体が、オイルまたはスチームを用いるオイル式またはスチーム式の赤外線ヒーターは、有機溶剤が共存する雰囲気における防爆の観点で好ましい。セルロースアシレートフイルムの温度は、アルカリ溶液処理前に加熱した温度と同じでも異なっていてもよい。また、鹸化反応中に温度を連続的、または段階的に変更してもよい。フイルム温度の検出には、一般に市販されている非接触の赤外線温度計が利用でき、上記温度範囲に制御するために、加熱手段に対してフィードバック制御を行ってもよい。
【００６７】
本発明においては、とくにセルロースアシレートフイルムを搬送しながら鹸化処理を実施することが好ましい。フイルムの搬送速度は、上記アルカリ溶液の組成と塗布方式の組み合わせによって決定する。一般に、１０〜５００ｍ／分が好ましく、２０〜３００ｍ／分がさらに好ましい。搬送速度に応じて、安定な塗布操作が行えるように、アルカリ溶液の物性（比重、粘度、表面張力）、塗布方式および塗布操作条件を決定する。
【００６８】
アルカリ溶液とセルロースアシレートフイルムとの鹸化反応を停止するには、３つの方法がある。一つは、塗布されたアルカリ溶液を希釈してアルカリ濃度を下げ、反応速度を低下させる方法であり、二つ目は、アルカリ溶液が塗布されたセルロースアシレートフイルムの温度を下げ、反応速度を低下させる方法であり、三つ目は、酸性の液によって中和する方法である。
【００６９】
塗布されたアルカリ溶液を希釈するためには、希釈液を塗布する方法、希釈液を吹き付ける方法、あるいは、希釈液の入った容器にセルロースアシレートフイルムごと浸漬する方法が採用できる。中でも希釈液を塗布する方法と吹き付ける方法がセルロースアシレートフイルムを連続搬送しながら実施する上で好ましい方法である。希釈液を塗布する方法は、必要最小限の希釈液量を用いて実施できるために最も好ましい。
【００７０】
希釈液の塗布は、既にアルカリ溶液が塗布されたセルロースアシレートフイルム上に希釈液を再度適用できる連続塗布可能な方式であることが望ましい。塗布方法は、前記した鹸化処理工程で記載した内容と同様のものが挙げられる。アルカリ溶液と希釈液とを速やかに混合してアルカリ濃度を低下させるためには、希釈液が塗布される微小領域（塗布ビードと呼ぶこともある）において、流れが層流であるダイコーターよりも、流れが一様とならないロールコーターやロッドコーターが好ましい。
【００７１】
希釈液は、セルロースアシレートフイルムを溶解したり膨潤したりすることなく、アルカリ濃度を低下させることが目的であるため、アルカリ溶液中のアルカリ剤を溶解する液でなければならない。したがって、その溶媒としては水または有機溶剤と水との混合液を用いる。有機溶剤は単独でも２種以上を併用してもよく、希釈液としてセルロースアシレートフィルムを溶解若しくは膨潤しない割合で任意に用いることができる。
【００７２】
希釈液の塗布量は、アルカリ溶液の濃度に応じて決定する。塗布ビードにおける流れが層流であるダイコーターの場合、塗布量は、元のアルカリ濃度を１．５〜１０倍に希釈することが好ましく、２乃至５倍に希釈することがさらに好ましい。ロールコーターやロッドコーターの場合は、塗布ビード内の流動が一様でないため、アルカリ溶液と希釈溶媒との混合が発生し、この混合した液が再塗布される。したがって、この場合は希釈溶媒の塗布量によって希釈率を特定することができないため、希釈溶媒塗布後のアルカリ濃度を測定する。ロールコーターやロッドコーターにおいても、塗布量は、元のアルカリ濃度を１．５〜１０倍に希釈することが好ましく、２〜５倍に希釈することがさらに好ましい。
【００７３】
アルカリによる鹸化反応を迅速に停止するため、酸を用いることもできる。少ない量で中和するため、強酸を用いることが好ましい。さらに、水洗の容易さを考慮すると、アルカリと中和反応後に生成する塩が水に対する溶解度が高い酸を選択することが好ましい。塩酸、硝酸、リン酸、硫酸、クロム酸及びメタンスルホン酸が特に好ましい。
【００７４】
塗布されたアルカリ溶液を酸で中和するためには、酸溶液を塗布する方法、酸溶液を吹き付ける方法、あるいは酸溶液の入った容器にフイルムごと浸漬する方法が採用できる。酸溶液を塗布する方法と吹き付ける方法がフイルムを連続搬送しながら実施する上で好ましい。酸溶液を塗布する方法は、必要最小限の酸溶液を用いて実施できるために最も好ましい。
【００７５】
酸溶液の塗布は、既にアルカリ溶液が塗布されたセルロースアシレートフイルム上に酸溶液を再度適用できる連続塗布可能な方式であることが望ましい。塗布方式に関しては前記した鹸化処理で記載の内容と同様である。アルカリ溶液と酸溶液とを速やかに混合してアルカリを中和させるためには、ロールコーターやロッドコーターが好ましい。
【００７６】
酸溶液の塗布量は、アルカリの種類とアルカリ溶液の濃度に応じて決定する。塗布ビードにおける流れが層流であるダイコーターの場合、酸の塗布量は、元のアルカリ塗布量の０．１〜５倍であることが好ましく、０．５〜２倍であることがさらに好ましい。ロールコーターやロッドコーターの場合は、塗布ビード内の流動が一様でないため、アルカリ溶液と酸溶液との混合が発生し、混合した液が再塗布される。したがって、この場合は酸溶液の塗布量によって中和率を特定することができないため、酸溶液塗布後のアルカリ濃度を測定する必要がある。ロールコーターやロッドコーターにおいては、酸溶液塗布後のｐＨが４〜９になるように酸溶液の塗布量を決定することが好ましく、ｐＨ６〜８になるように決定することがさらに好ましい。
【００７７】
セルロースアシレートフイルムの温度を降下させて、鹸化反応を停止することもできる。反応を促進させるために室温以上に保たれた状態から、充分に温度低下させることによって実質的に鹸化反応を停止させる。フイルムの温度を低下させる手段は、セルロースアシレートフイルムの片面が濡れていることを考慮して決定する。塗布の反対面への冷風の吹き付け、あるいは、冷却ロールによる接触伝熱が好ましく採用できる。冷却後のフイルム温度は、０〜６０℃であることが好ましく、５〜５０℃であることがさらに好ましく、１０〜３０℃であることがが最も好ましい。フイルム温度は、非接触式の赤外線温度計で測定することが好ましい。測定した温度から、冷却手段に対してフィーッドバック制御を行い、冷却温度を調節することもできる。温度低下手段は，上記の希釈液で希釈する方法、或いは中和する方法と併用してもよい。
【００７８】
水洗工程は、アルカリ溶液を完全に除去するために実施する。又、中和の手段を用いた場合は、中和により生じた塩類等の組成物を完全に除去するために実施する。アルカリ溶液の組成物或いは中和による生成塩類等が残っていると、鹸化反応が進行するばかりでなく、後に塗布する配向膜ならびに液晶性分子層の塗膜形成や液晶分子の配向に影響を及ぼす。
水洗は、水を塗布する方法、水を吹き付ける方法、あるいは、水の入った容器にポリマーフイルムごと浸漬する方法で実施できる。
【００７９】
水吹きつけ方法は、塗布ヘッド（例、ファウンテンコーター、フロッグマウスコーター）を用いる方法、あるいは、空気の加湿や塗装、タンクの自動洗浄に利用されるスプレーノズルを用いる方法で実施できる。塗布方式に関しては、「コーティングのすべて」荒木正義編集、（株）加工技術研究会（１９９９年）に記載がある。円錐状あるいは扇状のスプレーノズルをフイルムの幅方向に配列して、全幅に水流が衝突するように配置することができる。市販のスプレーノズル（例えば、（株）いけうち製、スプレーイングシステムズ社製）を用いてもよい。
【００８０】
水の吹き付け速度は、大きい方が高い乱流混合が得られる。ただし、速度が大きいと、連続搬送するセルロースアシレートフイルムの搬送安定性を損なう場合もある。吹き付けの衝突速度は、５０〜１０００ｃｍ／秒が好ましく、１００〜７００ｃｍ／秒がさらに好ましい。
用いたアルカリ性塗布液のアルカリ濃度や副次添加物、溶媒の種類にもよるが、少なくとも１００〜１０００倍、好ましくは５００〜１万倍、さらに好ましくは１０００〜十万倍の希釈が得られる水洗水を使用する。
【００８１】
水洗で一定量の水を用いる場合、一度に全量適用するよりも数回に分割して適用する回分式洗浄方法が好ましい。すなわち、水の量を幾つかに分けて、フイルムの搬送方向にタンデムに設置した複数の水洗手段に供給する。一つの水洗手段と次の水洗手段との間には適当な時間（距離）を設けて、拡散によるアルカリ性塗布液の希釈を進行させる。さらに好ましくは、搬送されるポリマーフイルムに傾斜を設けるなどして、フイルム上の水がフイルム面に沿って流れる様にすれば、拡散に加えて、流動による混合希釈が得られる。最も好ましい方法としては、水洗手段と水洗手段の間にフイルム上の水膜を除去する水切り手段を設けることで、更に水洗希釈効率を高められる。具体的な水切り手段としては、ブレードコーターに用いられるブレード、エアナイフコーターに用いられるエアナイフ、ロッドコーターに用いられるロッド、ロールコーターに用いられるロールが挙げられる。
タンデムに配置された水洗手段の数は、多い方が有利である。ただし、設置スペースならびに設備コストの観点から、通常は２〜１０段、好ましくは２〜５段が使用される。
【００８２】
水切り手段後の水膜厚みは、薄い方が好ましいが、用いる水切り手段の種類によって最低水膜厚みが制限される。ブレード、ロッド、ロールなど、物理的に固体をフイルムに接触させる方法においては、例え固体がゴムなどの硬度の低い弾性体であったとしても、フイルム表面にキズを付けたり、弾性体が磨り減ったりするので有限の水膜を潤滑流体として残す必要がある。通常は、数μｍ以上、好ましくは１０μｍ以上の水膜を潤滑流体として残存させる。
【００８３】
極限まで水膜厚みを減少させられる水切り手段としては、エアナイフが好ましい。充分な風量と風圧を設定することにより、水膜厚みをゼロに近づけることが出来る。ただし、エアの吹出し量が大きすぎると、ばたつきや寄りなど、セルロースアシレートフイルムの搬送安定性に影響を及ぼすことがあるので、好ましい範囲が存在する。その範囲は、セルロースアシレートフイルム上の元の水膜厚み、フイルムの搬送速度にもよるが、通常は１０〜５００ｍ／秒、好ましくは２０〜３００ｍ／秒、より好ましくは３０〜２００ｍ／秒の風速を使用する。また、均一に水膜除去を行うためには、セルロースアシレートフイルムの幅方向の風速分布を、通常は１０％以内、好ましくは５％以内になるよう、エアナイフの吹出し口やエアナイフへの給気方法を調整する。搬送するセルロースアシレートフイルム表面とエアナイフ吹出し口の間隙は、狭い方が水切り能が増すが、セルロースアシレートフイルムと接触して傷付ける可能性が高くなるため、適当な範囲がある。そのため、通常は、１０μｍ〜１０ｃｍ、好ましくは１００μｍ〜５ｃｍ、さらに好ましくは５００μｍ〜１ｃｍの間隙をもって、エアナイフを設置する。さらに、エアナイフと対向する様に、フイルムの水洗面と反対側にバックアップロールを設置することで、間隙の設定が安定するとともに、フイルムのバタツキやシワ、変形などの影響を緩和することができるために好ましい。
【００８４】
水洗水には、純水を用いることが好ましい。本発明に用いられる純水とは、比電気抵抗が少なくとも１ＭΩ以上であり、特にナトリウム、カリウム、マグネシウム、カルシウムなどの金属イオンは１ｍｇ／Ｌ未満、塩素、硝酸などのアニオンは０．１ｍｇ／Ｌ未満を指す。純水は、逆浸透膜、イオン交換樹脂、蒸留などの単体、あるいは組み合わせによって、容易に得ることができる。
【００８５】
洗浄水の温度は、高い方が洗浄能力が上がる。しかし、搬送されるセルロースアシレートフイルム上に水を吹き付ける方法においては、空気と接触する水の面積が大きく、高温ほど蒸発が著しくなるため、周囲の湿度が増し、結露する危険性が高くなる。このため、洗浄水の温度は、通常は５〜９０℃、好ましくは２５℃〜８０℃、さらに好ましくは２５℃〜６０℃の範囲で設定する。
【００８６】
アルカリ性塗布液の成分、または鹸化反応の生成物が水に容易に溶けない場合、水洗工程の前または後に水に不溶な成分を除去するための溶剤洗浄工程を付加しても良い。溶剤洗浄工程は上に述べた水洗方法、水切り手段，又用いる溶剤は上記希釈液に記載と同様のものを利用することができる。
【００８７】
水洗工程の次に乾燥工程を実施することもできる。通常は、エアナイフなどの水切り手段で十分に水膜を除去できるため、乾燥工程は必要ないが、セルロースアシレートフイルムをロール状に巻き取る前に、好ましい含水率に調整するために加熱乾燥してもよい。逆に、設定された湿度を有する風で調湿することもできる。
【００８８】
［鹸化セルロースアシレートの用途］
本発明の方法で作製されたアルカリ鹸化セルロースアシレートの用途について簡単に述べる。
本発明の光学フィルムは、特に偏光板保護フィルム用として有用である。偏光板保護フィルムとして用いる場合、偏光板の作製方法は特に限定されず、一般的な方法で作製することができる。セルロースアシレートフィルムをアルカリ処理し、ポリビニルアルコールフィルムを沃素溶液中に浸漬延伸して作製した偏光子の両面に完全ケン化ポリビニルアルコール水溶液を用いて貼り合わせる方法がある。アルカリ処理の代わりに特開平６−９４９１５号、特開平６−１１８２３２号に記載されているような易接着加工を施してもよい。
【００８９】
保護フィルム処理面と偏光子を貼り合わせるのに使用される接着剤としては、例えば、ポリビニルアルコール、ポリビニルブチラール等のポリビニルアルコール系接着剤や、ブチルアクリレート等のビニル系ラテックス等が挙げられる。偏光板は偏光子及びその両面を保護する保護フィルムで構成されており、更に該偏光板の一方の面にプロテクトフィルムを、反対面にセパレートフィルムを貼合して構成される。プロテクトフィルム及びセパレートフィルムは偏光板出荷時、製品検査時等において偏光板を保護する目的で用いられる。この場合、プロテクトフィルムは、偏光板の表面を保護する目的で貼合され、偏光板を液晶板へ貼合する面の反対面側に用いられる。又、セパレートフィルムは液晶板へ貼合する接着層をカバーする目的で用いられ、偏光板を液晶板へ貼合する面側に用いられる。
【００９０】
液晶表示装置には通常２枚の偏光板の間に液晶を含む基板が配置されているが、本発明の光学フィルムを適用した偏光板保護フィルムはどの部位に配置しても優れた表示性が得られる。特に液晶表示装置の表示側最表面の偏光板保護フィルムには透明ハードコート層、防眩層、反射防止層等が設けられるため、該偏光板保護フィルムをこの部分に用いることが特に好ましい。
【００９１】
本発明のセルロースアシレートフィルムは、様々な用途で用いることができ、液晶表示装置の光学補償シートとして用いると特に効果がある。本発明のセルロースアシレートフィルムは、様々な表示モードの液晶セルに用いることができる。ＴＮ（Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＩＰＳ（Ｉｎ−Ｐｌａｎｅ Ｓｗｉｔｃｈｉｎｇ）、ＦＬＣ（Ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）、ＡＦＬＣ（Ａｎｔｉ−ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）、ＯＣＢ（Ｏｐｔｉｃａｌｌｙ Ｃｏｍｐｅｎｓａｔｏｒｙ Ｂｅｎｄ）、ＳＴＮ（Ｓｕｐｐｅｒ Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＶＡ（Ｖｅｒｔｉｃａｌｌｙ Ａｌｉｇｎｅｄ）及びＨＡＮ（Ｈｙｂｒｉｄ Ａｌｉｇｎｅｄ Ｎｅｍａｔｉｃ）のような様々な表示モードが提案されている。また、上記表示モードを配向分割した表示モードも提案されている。セルロースアシレートフィルムは、いずれの表示モードの液晶表示装置においても有効である。また、透過型、反射型、半透過型のいずれの液晶表示装置においても有効である。本発明のセルロースアシレートフィルムを、ＴＮモードの液晶セルを有するＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。
【００９２】
本発明のセルロースアシレートフィルムを、ＳＴＮモードの液晶セルを有するＳＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。一般的にＳＴＮ型液晶表示装置では、液晶セル中の棒状液晶性分子が９０〜３６０度の範囲にねじられており、棒状液晶性分子の屈折率異方性（△ｎ）とセルギャップ（ｄ）との積（△ｎｄ）が３００〜１５００ｎｍの範囲にある。ＳＴＮ型液晶表示装置に用いる光学補償シートについては、特開２０００−１０５３１６号公報に記載がある。本発明のセルロースアシレートフィルムは、ＶＡモードの液晶セルを有するＶＡ型液晶表示装置の光学補償シートの支持体として特に有利に用いられる。本発明のセルロースアシレートフィルムは、ＯＣＢモードの液晶セルを有するＯＣＢ型液晶表示装置又はＨＡＮモードの液晶セルを有するＨＡＮ型液晶表示装置の光学補償シートの支持体としても有利に用いられる。
【００９３】
本発明のセルロースアシレートフィルムは、ＴＮ型、ＳＴＮ型、ＨＡＮ型、ＧＨ（Ｇｕｅｓｔ−Ｈｏｓｔ）型の反射型液晶表示装置の光学補償シートとしても有利に用いられる。これらの表示モードは古くから良く知られている。ＴＮ型反射型液晶表示装置については、特開平１０−１２３４７８号、ＷＯ９８４８３２０号、特許第３０２２４７７号の各公報に記載がある。
【００９４】
反射型液晶表示装置に用いる光学補償シートについては、ＷＯ００−６５３８４号に記載がある。本発明のセルロースアシレートフィルムは、ＡＳＭ（Ａｘｉａｌｌｙ Ｓｙｍｍｅｔｒｉｃ Ａｌｉｇｎｅｄ Ｍｉｃｒｏｃｅｌｌ ）モードの液晶セルを有するＡＳＭ型液晶表示装置の光学補償シートの支持体としても有利に用いられる。ＡＳＭモードの液晶セルは、セルの厚さが位置調整可能な樹脂スペーサーにより維持されているとの特徴がある。その他の性質は、ＴＮモードの液晶セルと同様である。ＡＳＭモードの液晶セルとＡＳＭ型液晶表示装置については、クメ（Ｋｕｍｅ）他の論文（Ｋｕｍｅ ｅｔ ａｌ．， ＳＩＤ ９８ Ｄｉｇｅｓｔ １０８９ （１９９８））に記載がある。以上述べてきたこれらの詳細なセルロースアシレートフィルムの用途は前記の公技番号 ２００１−１７４５中の４５頁〜５９頁に詳細に記載されている。
【００９５】
【実施例】
［実施例１］
（セルロースエステルフイルムＴＦ−１の作製）
下記表１の組成物をミキシングタンクに投入し、攪拌して各成分を溶解し、セルロースアセテート溶液Ａを調製した。
【００９６】
【表１】

【００９７】
下記表２の組成物を分散機に投入し、攪拌して各成分を溶解し、マット剤溶液を調製した。
【００９８】
【表２】

【００９９】
下記表３の組成物をミキシングタンクに投入し、加熱しながら攪拌して、各成分を溶解し、レターデーション上昇剤溶液を調製した。
【０１００】
【表３】

【０１０１】
【化１】

【０１０２】
上記セルロースアセテート溶液Ａを９４．６質量部、マット剤溶液を１．３質量部、レターデーション上昇剤溶液４．１質量部それぞれを濾過後に混合し、バンド流延機を用いて流延した。レターデーション上昇剤のセルロースアセテートに対する質量比は４．６％であった。残留溶剤量３０％でフイルムをバンドから剥離し、１３０℃の条件で、残留溶剤量が１３質量％のフイルムをテンターを用いて２８％の延伸倍率で横延伸し、延伸後の幅のまま１４０℃で３０秒間保持した。その後、クリップを外して１４０℃で４０分間乾燥させセルロースアセテートフイルムを作製した。出来あがったセルロースアセテートフイルムの膜厚は８０μｍであった。
【０１０３】
（鹸化処理フイルムＳＦ−１の作製）
ロール幅１０００ｍｍの上記セルロースアセテートフイルムを、温度６０℃の誘電式加熱ロールを通過させ、フィルム表面温度４０℃に昇温した後に、下記表４に示す組成のアルカリ溶液（Ｓ−１）をロッドコーターを用いて塗布量１３．５ｃｃ／ｍ^２で塗布し、１１０℃に加熱した（株）ノリタケカンパニーリミテド製のスチーム式遠赤外ヒーターの下に１５秒滞留させた後に、同じくロッドコーターを用いて純水を３ｃｃ／ｍ^２塗布した。この時のフイルム温度は４０℃であった。次いで、ファウンテンコーターによる水洗とエアナイフによる水切りを３回繰り返した後に７０℃の乾燥ゾーンに５秒間滞留させて乾燥し、鹸化処理フイルムＳＦ−１を作製した。
アルカリ溶液（Ｓ−１）３５Ｌを使用して上記セルロースアセテートフィルム２０００ｍ^２を鹸化処理した。
【０１０４】
【表４】

【０１０５】
アルカリ溶液（Ｓ−１）の粘度は、５．５ｍＰａ・ｓ（温度２５℃）、表面張力は２２．５ｍＮ／ｍ（２５℃）であった。
【０１０６】
（比較用鹸化処理フイルムＳＦＲ−１の作製）
上記アルカリ溶液（Ｓ−１）の組成から界面活性剤（Ｋ−１）１．０質量％を除いた以外は、アルカリ溶液（Ｓ−１）と同じ組成の比較用処理液（ＳＲ−１）を調製し、この処理液を用いて上記鹸化処理フイルムＳＦ−１と同じ方法で比較用鹸化フィルムＳＦＲ−１を作製した。なお、アルカリ溶液（ＳＲ−１）の粘度は、５．５ｍＰａ・ｓ（温度２５℃）、表面張力は２２．６ｍＮ／ｍ（２５℃）であった。
【０１０７】
（比較用鹸化処理フイルムＳＦＲ−２の作製）
アルカリ溶液（Ｓ−１）の組成から相溶化剤を除いてその分を水及び有機溶媒に案分比例させて加えた下記表５の組成の比較用処理液（ＳＲ−２）を調製し、この処理液を用いて上記鹸化処理フイルムＳＦ−１の作製と同じ方法で比較用鹸化フィルムＳＦＲ−２を作製した。なお、アルカリ溶液（ＳＲ−２）の粘度は、３．５ｍＰａ・ｓ（温度２５℃）、表面張力は２２．０ｍＮ／ｍ（２５℃）であった。
【０１０８】
【表５】

【０１０９】
使用した上記アルカリ溶液（Ｓ−１，ＳＲ−１及びＳＲ−２）の性状と、作製した鹸化処理フィルム（ＳＦ−１，ＳＦＲ−１及びＳＦＲ−２）の性能を下記表６に示す。表中のＡ及びＢは、鹸化処理のスタート直後の試料をＡ，２０００ｍ^２処理後の試料をＢと表したもので、それぞれについて観察と評価を行なって表に示したものである。
【０１１０】
【表６】

【０１１１】
表６に記載の評価項目に１）〜４）の注記番号を付した各評価方法は以下のとおりである。
１）アルカリ溶液の性状
アルカリ溶液の透明性を目視で以下の基準を用いて評価した。
〇：濁りや沈殿が認められず、全く透明
×：濁りが発生
××：沈殿物が発生
【０１１２】
２）水との接触角
接触角計（協和界面科学（株）製、ＣＡ−Ｘ型接触角計）を用いて、乾燥状態（２０℃／６５％ＲＨ）で液体に純水を使用して直径１．０ｍｍの液滴を針先に作り、これをフィルムの表面に接触させて液滴を作った。固体液体が接する点における液体表面に対する接線と固体表面がなす角で、液体を含む方の角度を接触角とした。
各フィルムについて、１平方メートルの面内において両端及び中央の９箇所の接触角を測定し、上限値と下限値を記載した。ただし、±１度の範囲は測定におけるばらつきの範囲であり、その中央値で示した。
【０１１３】
３）ヘイズ
鹸化処理フイルムのヘイズの測定は、日本電色（株）社製ＮＨＤ１０１ＤＰ型光学試験機を用いて測定した。
４）異物、濁り
鹸化処理フイルムから全幅で長手方向に１ｍの長さに切りだし、この試料にシャウカステン上で光を透過させながら目視及びルーペで異物及び濁りの有無を観察し、以下の基準を用いて評価した。
〇：異物、濁りの発生が全く認められない（１０人で評価し、一人も認識できないレベル）
△：異物、濁りが弱く発生する（１０人で評価し、２〜５人が認識するレベル）
×：異物、濁りが強く発生する（１０人で評価し、６人以上が認識するレベル）
【０１１４】
表６に示すように、本発明の実施態様では２０００ｍ^２のフィルムを処理した後でもアルカリ溶液は透明であり、鹸化処理後のフィルム表面は、水との接触角が３０度となった。また、鹸化処理フィルムのヘイズも少なく異物や濁りの発生も全く認められなかった。
一方、比較溶アルカリ溶液（ＳＲ−１）及び（ＳＲ−２）は、２０００ｍ^２処理した後では濁りあるいは沈殿が発生した。
また、比較溶アルカリ鹸化処理フィルムＳＦＲ−１及びＳＦＲ−２は、鹸化処理のスタート直後（ＳＦＲ−１Ａ及びＳＦＲ−２Ａ）では、本発明のフィルムＳＦ−１とほぼ同等の性能が得られたが、２０００ｍ^２処理した時点の試料（ＳＦＲ−１Ｂ及びＳＦＲ−２Ｂ）では，いずれも水との接触角の面内でのばらつきが大きくなり、ヘイズ値も増大し、フィルム表面に濁り及び異物の発生が見られ、実用に供されるレベルではなかった。
【０１１５】
次ぎに、鹸化処理においてＡ部及びＢ部の両試料ともに良好な性能が得られた本発明のフィルムＳＦ−１を用いて、以下に述べるように光学フィルムを作製し、性能評価を行った。
【０１１６】
（配向膜の形成）
上記フイルムＳＦ―１の鹸化処理スタート直後の試料（ＳＦ−１Ａ）及び２０００ｍ^２処理した時点の試料（ＳＦ−１Ｂ）の鹸化処理面に下記構造の変性ポリビニルアルコール２０質量部、水３６０質量部、メタノール１２０質量部、ならびにグルタルアルデヒド０．５質量部からなる配向膜塗布液をロッドコーターで３０ｃｃ／ｍ^２塗布し、６０℃の温風で６０秒、さらに９０℃の熱風で１５０秒間、乾燥した後に搬送方向に鉛直に配置したベルベット布ラビングロールを用いて、ラビング処理を行って配向膜を形成した。
変性ホ゜リビニルアルコール
【０１１７】
【化２】

【０１１８】
（光学異方性層の形成）
試料ＳＦ−１Ａ及びＳＦ−１Ｂに形成した配向膜の上に、下記のディスコティック化合物４１．０１質量部、エチレンオキサイド変成トリメチロールプロパントリアクリレート（Ｖ＃３６０、大阪有機化学（株）製）１．２２質量部、多官能アクリレートモノマー（ＮＫエステル Ａ−ＴＭＭＴ 新中村化学工業製）２．８４質量部、セルロースアセテートブチレート（ＣＡＢ５５１−０．２、イーストマンケミカル社製）０．９０質量部、セルロースアセテートブチレート（ＣＡＢ５３１−１、イーストマンケミカル社製）０．２３質量部、光重合開始剤（イルガキュアー９０７、チバガイギー社製）１．３５質量部、増感剤（カヤキュアーＤＥＴＸ、日本化薬（株）製）０．４５質量部を、１０２質量部のメチルエチルケトンに溶解した後に＃４のワイヤーバーで塗布した。続き、連結する１３０℃の熱風ゾーンで２分間加熱し、円盤状化合物を配向させた。最後に８０℃の雰囲気下のもと、膜面温度が約１００℃の状態で１２０Ｗ／ｃｍ高圧水銀灯を用いて、０．４秒間ＵＶ照射しディスコティック化合物を重合させ、光学異方性層を形成した。波長６３３ｎｍで測定した光学異方性層のＲｅレターデーション値は４５ｎｍであった。また、円盤面と第１透明支持体面との間の角度（傾斜角）は平均で３９度であった。
【０１１９】
【化３】

【０１２０】
（光学補償シートの評価方法）
ヘイズ
得られたフイルムＳＦ−１〜ＳＦ−４及びＳＦＲ−１について、日本電色（株）社製ＮＨＤ？１０１ＤＰ型光学試験機を用いてヘイズの測定を行った。
透過光ムラ
各光学補償シートを、クロスニコルス配置した２枚の偏光板の間に挟み、透過光のムラを目視で観察し官能評価を行った。
○：全く発生しない（１０人が評価し、１人も認識できないレベル）
△ ：弱く発生する（１０人が評価し、１〜５人が認識するレベル）
× ：強く発生する（１０人が評価し、６人以上が認識するレベル）
密着性
各光学補償シートを３０ｃｍ×２５ｃｍに裁断し、２５℃相対湿度６０％の条件下で１日放置した後、光学異方性層側に幅１．２ｃｍ、長さ１０ｃｍのセロテープ（ニチバン社製Ｎｏ．４０５）を５枚貼り付け、１枚ずつ１秒間ではがし取り、フイルムと配向膜の間で剥離する状態を検査した。１０枚のセロテープの内、何枚に塗布層間の破壊が発生するかによって、相対的な密着性の優劣を評価した。
表７にこれらの評価結果を示す。
【０１２１】
【表７】

【０１２２】
表７に示されるように、本発明に従う鹸化処理を実施したＳＦ−１Ａ及びＳＦ−１Ｂともにヘイズが低く且つ透過光のムラは見られなく良好であった。又密着性も充分で良好であった。
以上のように、本発明の方法で作製した鹸化セルロースアシレート及びそれを用いた光学フィルムは、均一性に優れ、かつ密着性も良好な性能を示している。
【０１２３】
［実施例２］
（鹸化セルローストリアセテートフイルム）
セルローストリアセテートフイルム：フジタックＴＤ８０ＵＦ（富士写真フイルム（株）製）に１００℃の熱風を衝突させ、４５℃まで加熱した後に、２５℃に保温した下記内容のアルカリ溶液（Ｓ−２）をロッドコーターを用いて１４ｃｃ／ｍ^２ 塗布し、１３秒間経過後、再びロッドコーターを用いて純水を５ｃｃ／ｍ^２ 塗布した。この時のフイルム温度は４５℃であった。次いで、エクストルージョン型コーターを用いて１０００ｃｃ／ｍ^２ の純水を塗布し、水洗を行い、５秒間経過後に１００ｍ／秒の風をエアナイフより水塗布面に衝突させた。このエクストルージョンコーターによる水洗とエアナイフによる水切りを２回繰り返した後に８０℃の乾燥ゾーンに１０秒間滞留させて乾燥し、鹸化処理フイルムＳＦ−２を作製した。実施例１同様、２０００ｍ^２のフィルムを鹸化処理した。
【０１２４】
【表８】

【０１２５】
なお、アルカリ溶液（Ｓ−２）の粘度は、５．６ｍＰａ・ｓ（温度２５℃）、表面張力は２２．８Ｎ／ｍ（２５℃）であった。
【０１２６】
得られたフィルムの鹸化処理スタート時及び２０００ｍ^２処理した時の各フィルム試料（ＳＦ−２Ａ及びＳＦ−２Ｂ）表面の表面エネルギーを下記の方法で求めた結果、６０ｍＮ／ｍであった。
表面エネルギーは「ぬれの基礎と応用」（リアライズ社 １９８９．１２．１０発行）に記載の接触角法により求めた。表面エネルギーが既知の水及びヨウ化メチレンの２種類の溶液をセルロースアセテートフィルムに滴下し、液滴の表面とフィルム表面との交点において、液滴に引いた接線とフィルム表面のなす角で、液滴を含む方の角を接触角と定義し、計算によりフィルムの表面エネルギーを算出した。
【０１２７】
（偏光板）
延伸したポリビニルアルコールフイルムにヨウ素を吸着させて偏光膜を作製し、ポリビニルアルコール系接着剤を用いて、実施例１で作成した光学補償シートを偏光膜の片側に、もう一方には上記鹸化処理フィルムＳＦ−２Ａをホ゜リビニルアルコール系接着剤を用いて貼り付けた後、８０℃で１０分間乾燥させた。偏光膜の透過軸と実施例１で作製した光学補償シートの遅相軸とが平行になるように配置した。偏光膜の透過軸とセルローストリアセテートフイルムの遅相軸とは、直交するように配置した。このようにして偏光板を作製した。
又、鹸化処理フィルムＳＦ−２Ａの代わりに、ＳＦ−２Ｂを用いて、上記と同様にして偏光板を作製した。
【０１２８】
（液晶表示装置）
ＴＮ型液晶セルを使用した液晶表示装置（６Ｅ−Ａ３、シャープ（株）製）に設けられている一対の偏光板を剥がし、代わりに上記に作製した各偏光板を、実施例１で作製した光学補償シートが液晶セル側となるように粘着剤を介して、観察者側およびバックライト側に一枚ずつ貼り付けた。観察者側の偏光板の透過軸と、バックライト側の偏光板の透過軸とは、Ｏモードとなるように配置した。
【０１２９】
このようにして作製した液晶表示装置について、測定機（ＥＺ−Ｃｏｎｔｒａｓｔ １６０Ｄ、ＥＬＤＩＭ社製）を用いて、黒表示（Ｌ１）時の描画ムラを目視で観察した。
その結果、上記の本発明の方法による鹸化処理フィルムＳＦ−２Ａ又はＳＦ−２Ｂが保護フィルムとなるように設置したものは、両者とも画面全面が曇りの無い鮮明で高い輝度の画像が得られた。
以上の目視観察結果より、本発明の方法で長尺フィルムを鹸化処理したセルロースアシレートフィルムを用いたものは、良好な光学特性を有することが示された。
【０１３０】
実施例３
特開２００２−１８２０３３号公報の実施例１の記載に従って、反射防止膜を設けたセルロースアシレートフイルムを作製した。次に、このセルロースアシレートフイルムの防汚層の表面にポリエチレンテレフタレートフイルム（ＳＡＴ−１０６ＴＳ、（株）サンエイ化研製）を貼り合わせた。このフイルムを、浸漬処理装置として電子製版システム用のマスターエッチングプロセッサー：Ｅ−３８０℃を用いて、この装置に下記組成のアルカリ溶液（Ｓ−３）を入れて液温４５℃に設定した。フィルムの浸漬時間が１０秒間になるように浸漬した後、水に浸漬してアルカリ溶液を充分に洗い流した。次いで、０．５％希硫酸水溶液に１０秒間浸漬した後、水に浸漬して充分に洗浄した。さらにこのフイルムを１００℃で乾燥させて鹸化セルロースアシレートフィルム（ＳＦ−３）を作製した。ポリエチレンテレフタレートフイルムを、セルローストリアセテートフイルムから取り除き、第１偏光板保護膜を作製した。
【０１３１】
【表９】

【０１３２】
なお、アルカリ溶液（Ｓ−３）の粘度は、２．０ｍＰａ・ｓ（温度２５℃）、表面張力は３５．０ｍＮ／ｍ（２５℃）であった。
【０１３３】
（第２偏光板保護膜の作製）
上記方法で作製した別のセルローストリアセテートフイルムの一方の面にポリエチレンテレフタレートフイルム（ＳＡＴ−１０６ＴＳ、（株）サンエイ化研製）を貼り合わせた。第１偏光板保護膜の作製と同様に、鹸化処理を実施した後、ポリエチレンテレフタレートフイルムを取り除き、第２偏光板保護膜を作製した。
【０１３４】
（偏光板の作製）
厚さ７５μｍのポリビニルアルコールフイルム（クラレ（株）製）を、ヨウ素７質量部およびヨウ化カリウム１０５質量部を水１０００質量部に溶解した水溶液に５分間浸漬し、フイルムにヨウ素を吸着させた。次いで、フイルムを４０℃の４質量％ホウ酸水溶液中で、４．４倍に縦方向に１軸延伸をした後、緊張状態のまま乾燥して偏光膜を作製した。接着剤としてポリビニルアルコール系接着剤を用い、偏光膜の一方の面に第１偏光板保護膜のケン化処理されたセルローストリアセテートフイルムの表面を貼り合わせ、偏光膜のもう一方の面には、第２偏光板保護膜のケン化処理されたセルローストリアセテートフイルムの表面を貼り合わせた。このようにして偏光板を作製した。
【０１３５】
（偏光板の評価）
上記の方法で偏光板１００枚を作製し、それぞれ、アクリル系接着剤を用いてガラス板に貼り合わせ、それらを恒温恒湿槽に入れ、恒温恒湿槽内を７０℃、９３％ＲＨの雰囲気と２５℃、９３％ＲＨの雰囲気とに１２時間ずつ交互に設定変更しながら、のべ１０００時間の耐久性試験を行った。恒温恒湿槽から取り出した１００枚の試料について偏光板とガラス板の間の剥がれと泡の発生状況を調べところ、１００枚全てにおいて剥がれ及び泡の発生が認められなかった。
又、市販の薄膜トランジスタ（ＴＦＴ：ｔｈｉｎ−ｆｉｌｍ−ｔｒａｎｓｉｓｔｏｒ）型の液晶モニターの両面の偏光板を剥がし、上記の偏光板を両面に貼り合せ、黒表示と白表示のムラの有無を目視判定した。全画面にムラ等の視覚上の欠陥は全く見られなかった。
【０１３６】
実施例４
（鹸化セルローストリアセテートフイルム）
実施例３記載の反射防止膜をセルロースアシレートフィルムの片面に付設し、反射防止膜が塗布されていない側の面上に、８０℃の熱風を衝突させ、４５℃まで加熱した後に、３５℃に保温した下記表１０記載の組成の各アルカリ溶液（Ｓ４〜７）をロッドコーターを用いて塗布量５ｃｃ／ｍ^２で 塗布し、１０秒間経過後、再びロッドコーターを用いて純水を５ｃｃ／ｍ^２ 塗布した。この時のフイルム温度は４５℃であった。次いで、エクストルージョン型コーターを用いて１０００ｃｃ／ｍ^２ の純水を塗布することによって水洗を行い、５秒間経過後に１００ｍ／秒の風をエアナイフより吹き付けた。このエクストルージョンコーターによる水洗とエアナイフによる水切りを２回繰り返した後に８０℃の乾燥ゾーンに１０秒間滞留させて乾燥し、鹸化処理フイルムＳＦ−４〜ＳＦ−７を作製した。
【０１３７】
【表１０】

【０１３８】
なお、表４、５，８，９及び上記表１０中の有機溶媒の溶解度パラメーター（［ｍＪ／ｍ^３］^１／２）及びＩ／Ｏ値は、明細書中にも前記したが、以下に挙げておく。

各アルカリ溶液（Ｓ−４〜Ｓ−７）の粘度は、１．８〜６ｍＰａ・ｓ（温度２５℃）、表面張力は２０〜３０ｍＮ／ｍ（２５℃）であった。
【０１３９】
各フィルム（ＳＦ−４〜７）の水との接触角は、３０〜３５度の範囲であった。
次に、実施例３に用いた鹸化フィルムの代わりに、鹸化フィルムＳＦ−４〜ＳＦ−７を用いて偏光板を作製した。実施例３と同様にして偏光板の性能を評価した結果、実施例３の試料と同等の性能を示した。
【０１４０】
【発明の効果】
アルカリ剤、水、有機溶媒、相溶化剤及び界面活性剤を含有するアルカリ溶液を用いる本発明のセルロースアシレートフィルムのアルカリ鹸化方法によれば、フィルムにヘイズなどの欠陥を生じることなく、フィルム表面を均一かつ精度よくアルカリ鹸化することができ、しかも片面を選択的に高い生産性のもとに鹸化することができる。このアルカリ鹸化フィルムは、表示欠陥のない大きい面積の液晶表示装置用光学補償シートに容易に組み込むことができる。また、光学補償シートの透明支持体と配向膜との密着性に優れた透明支持体用セルソースアシレートフイルムが得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for alkali saponification of a cell source acylate film, a saponified cellulose acylate film, and an optical film using the same. In particular, the present invention relates to an optical film useful for polarization, light diffusion, optical compensation and the like for image display devices.
[0002]
[Prior art]
Various displays mounted on word processors, personal computers, televisions, various instruments, and the like can observe visual information such as letters and figures through a transparent protective substrate such as a glass or plastic plate on the surface. Recently, many of the displays of devices have become liquid crystal display devices. A liquid crystal display device usually comprises a liquid crystal cell, a polarizing plate, and an optical compensation sheet (retardation plate). In the transparent liquid crystal display device, two polarizing plates are attached to both sides of the liquid crystal cell, and one or two optical compensation sheets are disposed between the liquid crystal cell and the polarizing plate. The reflection type liquid crystal display device includes a reflection plate, a liquid crystal cell, one optical compensation sheet, and one polarizing plate.
[0003]
In a liquid crystal display device, one or two polarizing plates are used to display a liquid crystal image according to a signal. A polarizing plate usually protects a polarizing element film obtained by stretching and orienting a polyvinyl alcohol (hereinafter abbreviated as PVA) -based film adsorbed and dyed with iodine and / or a dichroic dye in a certain direction. It consists of a transparent protective film for polarizing plates.
In addition, polarizing plates using a cellulose acylate film as a protective film have excellent optical properties, high polarization in a wide wavelength range, and excellent brightness and contrast. Also widely used as a polarizing plate.
[0004]
As the optical compensation sheet, a stretched birefringent film for eliminating image coloring or expanding a viewing angle has been conventionally used.
Further, instead of an optical compensation sheet made of a stretched birefringent film, an optical compensation sheet having an optically anisotropic layer formed from a liquid crystalline molecule (particularly a discotic liquid crystalline molecule) on a transparent support may be used. Proposed. The optically anisotropic layer is formed by aligning liquid crystalline molecules and fixing the alignment state.
In general, by using liquid crystal molecules in the optical compensation sheet, it has become possible to realize optical characteristics that could not be obtained with conventional stretched birefringent films. The optical characteristics of the optical compensation sheet are provided by designing according to the difference in the optical properties of the liquid crystal cell and the display mode of the liquid crystal cell. When liquid crystalline molecules, particularly discotic liquid crystalline molecules are used for the optical compensation sheet, optical compensation sheets having various optical characteristics corresponding to various display modes of the liquid crystal cell can be produced.
[0005]
If an elliptically polarizing plate is formed by laminating an optical compensation sheet using liquid crystal molecules and a polarizing film, the optical compensation sheet can also function as one transparent protective film of the polarizing plate. Such an elliptically polarizing plate has a layer structure in which an optically anisotropic layer formed of a transparent protective film, a polarizing film, a transparent support, and liquid crystal molecules is laminated in this order. Since the liquid crystal display device is required to have a thin and lightweight characteristic, by using one of the components (for example, the transparent protective film of the polarizing plate and the support of the optical compensation sheet or the stretched birefringent film) If it can be reduced, the device can be made thinner and lighter. For example, Patent Documents 1 to 3 describe an integrated elliptical polarizing plate in which a transparent support of an optical compensation sheet using liquid crystal molecules and one protective film of a polarizing plate are used in common.
[0006]
A sheet-like material having optical functionality such as a polarizing plate and an optical compensation sheet as described above is called an optical film, but as a transparent support for the optical film, it has excellent light transmittance and optical non-orientation. Cellulose ester film typified by cellulose acetate film is used which has excellent physical and mechanical properties and has small dimensional change with respect to temperature and humidity change.
[0007]
A polarizing element and an optical compensation layer are provided on a cellulose ester film of a transparent support via a polarizing film and an alignment film (usually polyvinyl alcohol). A method for providing adhesion to these polarizing film and alignment film As one of the methods, there is known a method (for example, Patent Documents 4 to 7) in which a cellulose ester film is immersed in an alkaline solution to saponify and hydrophilize the surface.
[0008]
However, when these treatment solutions are treated with an aqueous solution containing only an alkali agent, there are problems such as that it takes time to saponify the film and that it is difficult to uniformly saponify the hydrophobic film surface. Also, in the saponification bath treatment by dipping, both sides of the cellulose ester film become hydrophilic at the same time, so if a hydrophilic layer such as polyvinyl alcohol is coated on one side and wound up in a roll shape, the front and back will adhere Problem occurs. As a means of hydrophilizing only one side in the saponification bath treatment, there is a method of applying saponification treatment to the non-target surface by waterproofing such as laminate, but not only complicated processes increase, but also unnecessary disposal This is not preferable from the viewpoint of productivity and environmental conservation.
[0009]
As a method for avoiding such an inconvenience, a method of immersing in an alkali solution containing an organic solvent that does not dissolve or swell the polymer film in the alkali solution (Patent Document 8), or an alkali There has been proposed a method (Patent Document 9) in which a solution is applied onto a film surface and at least one surface is saponified. By including an organic solvent in the alkaline solution, the saponification reaction activity can be increased as compared with a pure water solvent. However, depending on the type or content of the organic solvent, the additive substance contained in the film to be treated is eluted and haze is generated. The quality as an optical film may be deteriorated.
In addition, with the recent rapid development of large screens and mobile devices of image display devices, it is desired that long films can be produced continuously and more quickly and stably. In the case of continuous long coating, there is a tendency that it is difficult to obtain a uniform and stable saponification degree over the entire length of the film due to a change in composition of the coating solution.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-191217
[Patent Document 2]
JP-A-8-21996
[Patent Document 3]
JP-A-8-94838
[Patent Document 4]
Paragraph No. [0008] of Japanese Patent Laid-Open No. 7-151914
[Patent Document 5]
Paragraph No. [0033] of JP-A-8-94838
[Patent Document 6]
Paragraph number [0083] of Japanese Patent Laid-Open No. 2001-166146
[Patent Document 7]
Paragraph No. [0042] of JP 2001-188130 A
[Patent Document 8]
(Paragraph number [0034] of JP-A-2002-82226)
[Patent Document 9]
WO02 / 46809 Publication
[0011]
[Problems to be solved by the invention]
As described above, the conventional method for alkaline saponification of cellulose ester film does not yet have a saponification method that fully satisfies the demand, and a method for stably producing a long film with high productivity is desired. An object of the present invention is to provide an alkali saponification method for saponifying a cellulose ester film stably and uniformly over the entire surface by a rapid alkali saponification treatment.
Another object of the present invention is to provide a surface saponified cellulose ester film for easily producing a large area optical sheet free from display defects in an image display device.
Another object of the present invention is to provide a liquid crystal display device capable of displaying a clear image provided with an optical sheet having a cellulose ester film as a support.
[0012]
[Means for Solving the Problems]
The above-described problems of the present invention are achieved by the following alkaline saponification methods (1) to (10), a surface saponified film, and an optical film using the film.
(1) A method for alkali saponification of a cellulose acylate film, wherein the cellulose acylate film is alkali saponified using an alkali solution containing at least an alkali agent, water, an organic solvent, a surfactant and a compatibilizing agent.
(2) The organic solvent has an inorganic / organic value (I / O value) of 0.5 or more and a solubility parameter of 16 to 40 [mJ / m.³]^1/2The method for alkali saponification of a cellulose acylate film according to the above (1), characterized in that
[0013]
(3) In the above (1) or (2), the surfactant is at least one selected from nonionic surfactants, anionic surfactants, cationic surfactants and amphoteric surfactants. The alkali saponification method of the cellulose acylate film of description.
(4) The above (1) to (1), wherein the compatibilizing agent is at least one selected from polyol compounds having a water solubility of 30 g or more with respect to 100 g of the compatibilizing agent at a temperature of 25 ° C. The method for alkali saponification of a cellulose acylate film according to any one of 3).
(5) The above alkaline solution, wherein the alkali solution has an alkali agent concentration of 0.1 to 5 mol / Kg, a surface tension of 45 mN / m or less, and a viscosity of 0.8 to 20 mPa · s. The alkali saponification method of the cellulose acylate film in any one of-(4).
[0014]
(6) The alkali saponification method for a cellulose acylate film according to any one of (1) to (5) above, wherein the alkaline solution contains an antifoaming agent.
(7) A step of applying the alkali solution to the cellulose acylate film at room temperature or higher, a step of maintaining the cellulose acylate film carrying the alkali solution at room temperature or higher for at least 1 second, and the alkali solution to the cellulose acylate film. The method for alkaline saponification of a cellulose acylate film according to any one of the above (1) to (6), which comprises a step of washing off from the above.
(8) The cellulose acylate film is conveyed, and each step of alkali saponification is sequentially performed on one surface of the film to be conveyed, according to any one of (1) to (7), Alkaline saponification method.
[0015]
(9) A surface saponified cellulose acylate film obtained by the alkali saponification method according to any one of (1) to (8) above.
[0016]
(10) An optical film using the surface saponified cellulose acylate film described in (9).
[0017]
The surface saponified cellulose acylate film saponified with an alkali by any one of the above methods (1) to (8) is formed with an alignment film thereon, and then a liquid crystal molecule is applied on the alignment film. An optical compensation sheet can be produced by fixing the orientation of the film and forming an optically anisotropic layer.
In addition, the polarizing film is composed of a polarizing film and two transparent protective films disposed on both sides of the polarizing film, and one of the transparent protective films fixes the alignment film and the alignment of the liquid crystalline molecules on the cellulose acylate film. When the optically anisotropic layer is made of an optical compensation sheet provided in this order, the surface on the side on which the alignment film is applied as a cellulose acylate film by any one of the methods (1) to (8). Alkali saponified cellulose acylate films can be advantageously used. Therefore, an optical film excellent in interlayer adhesion and display surface uniformity can be produced using the cellulose acylate film.
The alkaline saponification method of the present invention is characterized in that the alkaline solution for saponification treatment is a solution containing at least an alkaline agent, water, an organic solvent, a surfactant and a compatibilizing agent, and by using this composition, The above-described saponification treatment can be speeded up and uniform saponification can be performed without defects such as non-uniform saponification degree, generation of haze, and local change in thickness.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
[Polymer film]
The polymer film preferably has a light transmittance of 80% or more. It is preferable that the polymer film hardly exhibits birefringence due to external force.
The polymer contains a hydrolyzable bond (bond to be saponified) such as an ester bond or an amide bond. In particular, it is preferable to include an ester bond, and it is more preferable that the ester bond is present in the side chain of the polymer. As the polymer in which the ester bond is present in the side chain, cellulose ester (hereinafter also referred to as cellulose acylate) is most preferable, and this is the support subject to the present invention.
[0019]
Hereinafter, cellulose acylate will be described in detail. Examples of the raw material cellulose include cotton linter and wood pulp. Any cellulose acylate obtained from any raw material cellulose may be used, or a mixture thereof may be used. In the cellulose acylate used in the present invention obtained from these celluloses, the degree of substitution of the cellulose with a hydroxyl group satisfies all of the following formulas (I) to (III).
[0020]
Formula (I): 2.6 ≦ SA ′ + SB ′ ≦ 3.0
Formula (II): 2.0 ≦ SA ′ ≦ 3.0
Formula (III): 0 ≦ SB ′ ≦ 0.8
[0021]
Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents. SA represents an acetyl group substituting a hydrogen atom of a hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting a hydrogen atom of a hydroxyl group of cellulose.
Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.7 to 2.96, and particularly preferably 2.80 to 2.95. Further, the substitution degree (SB ′) of SB is 0 to 0.8, particularly 0 to 0.6. Further, 28% or more of SB is preferably a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, more preferably 31% or more, and particularly 32% or more is 6%. It is also preferable that it is a substituent of a coordinate hydroxyl group. Furthermore, the cellulose acylate film in which the sum of the substitution degrees of SA and SB at the 6-position of cellulose acylate is 0.8 or more, more preferably 0.85 or more, and particularly preferably 0.90 or more. Can be mentioned. These cellulose acylate films can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can produce a good solution.
[0022]
The acyl group (SB) having 3 to 22 carbon atoms of the cellulose acylate used in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. The cellulose acylate is, for example, an alkyl carbonyl ester, an alkenyl carbonyl ester, an aromatic carbonyl ester, an aromatic alkyl carbonyl ester, or the like of cellulose, and each may further have a substituted group. These preferred SBs include propionyl group, butanoyl group, keptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, preferable SB is propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like.
[0023]
The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method includes a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specific examples include the methods described in JP-A-6-32801, JP-A-7-70202, JP-A-10-45804, JP-A-10-511728, JP-A-2001-200901, and the like.
[0024]
The degree of polymerization (viscosity average) of the cellulose acylate used in the present invention is preferably from 200 to 700, and particularly preferably from 250 to 550. In general, in order to satisfy the mechanical strength of cellulose acylate films, fibers or molded articles containing cellulose triacetate, it is necessary that the degree of polymerization is 200 or more. It is described in Asakura Shobo (1958), Jun Marusawa and Kazuo Uda “Plastic Materials Course 17”, Nikkan Kogyo Shimbun (1970).
[0025]
The cellulose acylate film used in the present invention may contain other compounds together with the above-mentioned cellulose acylate depending on the purpose and application of use.
[0026]
When a cellulose acylate film is used for an optical compensation sheet, the in-plane retardation (Re retardation) value and the thickness direction retardation (Rth retardation) value of the film are represented by the following formulas (I) and (II), respectively. Defined by
(I) Re = | nx−ny | × d
(II) Rth = ((nx + ny) / 2−nz) × d
In the formulas (I) and (II), nx is the refractive index in the slow axis direction in the film plane (direction in which the refractive index is maximum), and ny is the fast axis direction in the film plane (the refractive index is minimum). Nz is the refractive index in the thickness direction of the film, and d is the thickness of the film with the unit of nm.
The cellulose acylate film preferably has an Re retardation value of 1 to 200 nm and an Rth retardation value of 70 to 400 nm. A specific value is obtained by extrapolating from a measurement result in which the incident direction of the measurement light is inclined with respect to the vertical direction of the film film surface. The measurement can be performed using an ellipsometer (for example, M-150, manufactured by JASCO Corporation). As a measurement wavelength, 632.8 nm (He—Ne laser) is adopted.
[0027]
In order to adjust the retardation of the cellulose acylate film, a method of applying an external force such as stretching is generally used, but a retardation increasing agent for adjusting optical anisotropy is optionally added. In order to adjust the retardation of the cellulose acylate film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples thereof include compounds described in European Patent 0911656A2, JP-A Nos. 2000-1111914 and 2000-275434.
[0028]
The cellulose acylate used in the present invention is further added with various additives (for example, plasticizers, ultraviolet inhibitors, deterioration inhibitors, fine particles, release agents, infrared absorbers, antistatic agents, etc.) according to the application. They can be added and they can be solid or oily. Moreover, when a cellulose acylate film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For these details, materials described in detail on pages 16 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association) are preferably used. The amount of these additives to be used is not particularly limited as long as the added amount of each material exhibits its function, but may be appropriately used in the range of 0.001 to 20% by mass in the entire cellulose acylate composition. preferable.
[0029]
The cellulose acylate film according to the present invention is preferably formed by a solvent cast method.
Examples of the solvent to be used include conventionally known solvents, and those having a solubility parameter in the range of 17 to 22, for example, are preferable. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, fat having 5 to 8 carbon atoms Group hydrocarbons and aromatic hydrocarbons having 6 to 12 carbon atoms. Specifically, for example, detailed compounds can be mentioned on pages 12 to 16 of the aforementioned public technical number 2001-1745.
[0030]
In particular, it is preferable from the viewpoint of the solubility of cellulose acylate to use 20 to 90% by mass of acetate, 5 to 60% by mass of ketones, and 5 to 30% by mass of alcohols.
Examples of non-halogen organic solvent systems that do not contain halogenated hydrocarbons include paragraph numbers [0021] to [0025] of JP-A No. 2002-146043 and paragraph numbers of JP-A No. 2002-146045 [ Examples of solvent systems described in [0016] to [0021] and the like.
[0031]
Regarding the preparation of the cellulose acylate solution (dope) according to the present invention, the dissolution method is not particularly limited, and may be a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, or a combination thereof. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP-A-2000-53784, Kaihei 11-322946, JP-A-11-322947, JP-A-2-276830, JP-A-2000-273239, JP-A-11-71463, JP-A-04-259511, JP-A-2000-273184, JP-A-11-323017, JP-A-11-323017 11-302388 describes a method for preparing a cellulose acylate solution. The above-described method for dissolving cellulose acylate in an organic solvent is applicable to the present invention as long as it is within the scope of the present invention. Further, the dope solution of cellulose acylate is usually concentrated and filtered, and similarly described in detail on page 25 of the aforementioned technical number 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.
[0032]
Next, in the present invention, a method for producing a film using a cellulose acylate solution will be described. As a method and equipment for producing a cellulose acylate film, a conventionally known solution casting film forming method and solution casting film forming apparatus called a drum method or a band method used for producing a cellulose triacetate film are used. The film forming process will be described by taking the band method as an example. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in the storage kettle, and the bubbles contained in the dope are defoamed to finish. Prepare. The prepared dope is fed from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the rotational speed, and the dope is run endlessly from the die (slit) of the pressure die. The dope film (also referred to as a web) is peeled off from the metal support at the peeling point where the metal support is almost cast around the metal support. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. Each of these manufacturing processes (casting (including co-casting), metal support, drying, peeling, stretching, etc.) is described in detail on pages 25 to 30 of the aforementioned technical number 2001-1745. The contents made are mentioned. In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially.
[0033]
The retardation of the cellulose acylate film can be further adjusted by a stretching treatment. The draw ratio is preferably 3 to 100%.
The thickness of the cellulose acylate film is preferably 15 to 500 μm, more preferably 20 to 200 μm.
[0034]
[Alkaline solution]
The surface saponified cellulose acylate film of the present invention is characterized by being saponified using an alkaline solution containing at least an alkali agent, water, a surfactant and a compatibilizing agent.
Examples of the alkali agent include tribasic sodium phosphate, potassium, ammonium, dibasic sodium phosphate, potassium, ammonium, ammonium carbonate, ammonium bicarbonate, sodium borate, potassium, ammonium, sodium hydroxide. Inorganic alkaline agents such as potassium, lithium and ammonium. Moreover, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, Ethyleneimine, ethylenediamine, pyridine, DBU (1,8-diazabicyclo [5,4,0] -7-undecene), DBN (1,5-diazabicyclo [4,3,0] -5-nonene), tetramethylammonium Hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, triethylbutylammonium hydroxide Organic alkali agents such as Rokishido be used. These alkali agents can be used alone or in combination of two or more, and a part of them may be added in the form of a salt, for example, halogenated.
Among these alkali agents, sodium hydroxide and potassium hydroxide are preferable. The reason is that the pH can be adjusted in a wide pH range by adjusting these amounts.
[0035]
The concentration of the alkaline solution is determined according to the type of alkaline agent used, the reaction temperature, and the reaction time. In order to complete the saponification reaction in a short time, it is preferable to prepare a solution at a high concentration. However, if the alkali concentration is too high, the stability of the alkaline solution is impaired, and it may be precipitated during long-time application. The content of the alkali agent is preferably 0.1 to 5 moL / Kg, more preferably 0.5 to 3 moL / Kg in the alkaline solution.
[0036]
The solvent of the alkaline solution of the present invention is a mixed solution of water and an organic solvent. Any organic solvent that is miscible with water can be used.
Among these, a preferable organic solvent has an inorganic / organic value (I / O value) of 0.5 or more and a solubility parameter of 16 to 40 [mJ / m.³]^1/2The thing of the range of is preferable. More preferably, the I / O value is 0.6 to 10 and the solubility parameter is 18 to 31 [mJ / m.³]^1/2It is. If the I / O value is more inorganic than this range or the solubility parameter is low, the alkali saponification rate decreases, and the overall uniformity of the saponification degree becomes unsatisfactory. On the other hand, when the I / O value is on the organic side of the above range or the solubility parameter is highly soluble, the saponification rate is fast, but haze is likely to occur. Dissatisfied.
Examples of organic solvents that have solubility parameters and I / O values within the above ranges and can be preferably used in the present invention include the following solvents.

In addition, when an organic solvent, particularly an organic solvent in each of the above organic and soluble ranges, is used in combination with a compatibilizer and a surfactant described later, a high saponification rate is maintained and the saponification degree is uniform over the entire surface. Improves.
[0037]
Examples of the organic solvent having preferable characteristic values include those described in “Synthetic Organic Chemistry Association”, “New Edition Solvent Pocket Book” (Ohm Co., Ltd., published in 1994) and the like. (In addition, the inorganic / organic value (I / O value) of the organic solvent is described in, for example, Yoshio Tanaka, organic conceptual diagram) published in Sankyo Publishing Co., Ltd., 1983, pages 1-31).
[0038]
Specifically, monohydric aliphatic alcohols (eg, methanol, ethanol, propanol, butanol, pentanol, hexanol, etc.), alicyclic alkanols (eg, cyclohexanol, methylcyclohexanol, methoxycyclohexanol, cyclohexylmethanol, Cyclohexylethanol, cyclohexylpropanol, etc.), phenylalkanols (eg, benzyl alcohol, phenylethanol, phenylpropanol, phenoxyethanol, methoxybenzyl alcohol, benzyloxyethanol, etc.), heterocyclic alkanols (furfuryl alcohol, tetrahydrofurfuryl alcohol) Etc.), monoethers of glycol compounds (methyl cellosolve, ethyl cellosolve, propyl cellosolve, methoxymethoxyethane) Butyl cell sorb, hexyl cell sorb, methyl carbitol, ethyl carbitol, propyl carbitol, butyl carbitol, methoxy triglycol, ethoxy triglycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl Ethers, etc.) ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), amides (eg, N, N-dimethylformamide, dimethylformamide, N-methyl-2-pyrrolidone, 1,3 dimethylimidazolidinone, etc.) , Sulfoxides (eg, dimethyl sulfoxide) and ethers (eg, tetrahydrofuran, pyran, dioxane, trioxane, dimethyl cellosolve, diethyl cellosolve, dip Piruserusorubu, methyl ethyl cellosolve, dimethyl carbitol, dimethyl carbitol, methyl ethyl carbitol, etc.) and the like. The organic solvent to be used may be used alone or in combination of two or more.
[0039]
When at least one organic solvent is used alone or in combination of two or more organic solvents, those having high solubility in water are preferable. The solubility of water in the organic solvent is preferably 50% by mass or more, and more preferably freely mixed with water. An alkaline solution having sufficient solubility in an alkali agent, a salt of a fatty acid by-produced by a saponification treatment, a carbonate salt generated by absorbing carbon dioxide in the air, and the like can be prepared.
The use ratio of the organic solvent in the solvent is determined according to the type of solvent, miscibility with water (solubility), reaction temperature and reaction time. In order to complete the saponification reaction in a short time, it is preferable to prepare a solution at a high concentration. However, if the solvent concentration is too high, components (such as a plasticizer) in the acylate film may be extracted or excessive swelling of the film may occur, and it is necessary to select appropriately.
The mixing ratio of water and organic solvent is preferably 3/97 to 85/15 mass ratio. More preferably, it is 5 / 95-60 / 40 mass ratio, More preferably, it is 15 / 85-40 / 60 mass ratio. In this range, the entire film surface can be easily saponified uniformly without impairing the optical properties of the acylate film.
[0040]
The organic solvent contained in the alkaline solution used in the present invention reduces the haze, which is the object of the present invention, and coexists in addition to the organic solvent having the effect of increasing the uniformity and stability of the saponification degree. The organic solvent which has the effect | action of the solubilizing agent of the surfactant in the alkaline solution mentioned later which can increase the effect of invention, a compatibilizer, and an antifoamer is also contained. The organic solvent having this function may be an organic solvent different from the organic solvent having a preferable I / O value described above. Preferred organic solvents having a dissolution aid function include, for example, N-phenylethanolamine and N-phenyldiethanolamine, fluorinated alcohols (for example, C_nF_{2n + 1}(CH₂)_kOH (n is an integer of 3 to 8, k is an integer of 1 or 2), 1,2,2,3,3-heptafluoropropanol, hexafluorobutanediol, perfluorocyclohexanol and the like. . The content of the organic solvent used for the purpose of the dissolution aid is preferably 0.1 to 5% with respect to the total weight of the working solution.
[0041]
The alkaline solution used in the present invention contains a surfactant. By adding a surfactant, the surface tension is lowered to facilitate coating, and the uniformity of the coating is increased to prevent repelling failure, and haze that is likely to occur in the presence of an organic solvent is suppressed. Progress evenly. The effect becomes particularly remarkable by the coexistence of a compatibilizer described later. There is no restriction | limiting in particular in surfactant used, Any of anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorochemical surfactant, etc. may be sufficient.
[0042]
Hereinafter, the surfactants that can be used in the present invention will be sequentially described.
(Anionic surfactant)
Examples of the anionic surfactant include fatty acid salts, abietic acid salts, hydroxyalkane sulfonic acid salts, alkane sulfonic acid salts, dialkyl sulfosuccinic acid ester salts, α-olefin sulfonic acid salts, linear alkyl benzene sulfonic acid salts, and branched alkyl benzene. Sulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylenealkylsulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt , Petroleum sulfonates, sulfated beef tallow oil, sulfate esters of fatty acid alkyl esters, alkyl sulfate esters, polyoxyethylene alkyl ether sulfate esters, fatty acids Noglyceride sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styrylphenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates Preferable examples include salts, partially saponified products of styrene / maleic anhydride copolymer, partially saponified products of olefin / maleic anhydride copolymer, and naphthalene sulfonate formalin condensates.
[0043]
(Cationic surfactant)
Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts such as tetrabutylammonium bromide, polyoxyethylene alkylamine salts, polyethylene polyamine derivatives, and the like.
[0044]
(Amphoteric surfactant)
Examples of amphoteric surfactants include carboxybetaines, alkylaminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, imidazolines, and the like.
[0045]
(Nonionic surfactant)
Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, Sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, Polyglycerol fatty acid partial esters, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, Fatty acid diethanol amides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides and the like.
[0046]
Specific examples thereof include, for example, polyethylene glycol, polyoxyethylene lauryl ether, polyoxyethylene nonyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene Oxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene behenyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearamide, polyoxy Ethylene oleamide, polyoxyethylene castor oil, polyoxyethylene ethylene abietic Ether, polyoxyethylene nonine ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene glyceryl monooleate, polyoxyethylene glyceryl monostearate, polyoxyethylene propylene glycol monostearate, oxyethyleneoxy Propylene block polymer, distyrenated phenol polyethylene oxide adduct, tribenzylphenol polyethylene oxide adduct, octylphenol polyoxyethylene polyoxypropylene adduct, glycerol monostearate, sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, etc. It is done. The weight average molecular weight of these nonionic surfactants is preferably from 300 to 50,000, particularly preferably from 500 to 5,000.
[0047]
In the present invention, among the nonionic surfactants, a compound represented by the following general formula (1) is preferable.
General formula (1): R¹-O (CH₂CHR²O)_l-(CH₂CHR³O)_m-(CH₂CHR⁴O)_n-R⁵
In general formula (1), R¹~ R⁵Each represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group, an alkynyl group, an aryl group, a carbonyl group, a carboxylate group, a sulfonyl group, or a sulfonate group.
Specific examples of the alkyl group include a methyl group, an ethyl group, and a hexyl group. Specific examples of the alkenyl group include a vinyl group and a propenyl group. Specific examples of the alkynyl group include An acetyl group, a propynyl group, etc. are mentioned, As a specific example of the said aryl group, a phenyl group, 4-hydroxyphenyl group, etc. are mentioned.
l, m, and n represent an integer of 0 or more. However, all of l, m, and n are not 0.
Specific examples of the compound represented by the general formula (1) include homopolymers such as polyethylene glycol and polypropylene glycol, copolymers of ethylene glycol and propylene glycol, and the like. The ratio of the copolymer is preferably 10/90 to 90/10 from the viewpoint of solubility in an alkaline solution. Of the copolymers, graft polymers and block polymers are preferable from the viewpoints of solubility in an alkali solution and ease of alkali saponification treatment.
[0048]
(Fluorosurfactant)
The fluorosurfactant refers to a surfactant containing a perfluoroalkyl group in the molecule. Examples of such fluorosurfactants include perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, anionic types such as perfluoroalkyl phosphates, amphoteric types such as perfluoroalkyl betaines, and perfluoroalkyls. Cation type such as trimethylammonium salt, perfluoroalkylamine oxide, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl group and hydrophilic group-containing oligomer, perfluoroalkyl group and lipophilic group-containing oligomer, perfluoroalkyl group, hydrophilic Nonionic types such as group and lipophilic group-containing oligomers, perfluoroalkyl groups, and lipophilic group-containing urethanes.
Among the above surfactants, those having “polyoxyethylene” can be read as polyoxyalkylenes such as polyoxymethylene, polyoxypropylene and polyoxybutylene, and these are also included in the surfactant. The The surfactants may be used alone or in combination of two or more as long as the effect is not impaired by the combined use.
[0049]
Among the above surfactants, in the present invention, the quaternary ammonium salts as the cationic surfactant, the various polyethylene glycol derivatives as the nonionic surfactant, the various polyethylene oxide adducts, and the like. Polyethylene oxide derivatives and betaine type compounds as amphoteric surfactants are preferred.
In the alkaline solution, it is also preferable to use a nonionic activator and an anionic activator or a nonionic activator and a cationic activator together in order to enhance the effect of the present invention.
[0050]
The amount of these surfactants added to the alkaline solution is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass, and particularly preferably 0.03 to 3% by mass. %. When the addition amount is less than 0.001% by mass, it is difficult to obtain the effect of adding the surfactant, and when it is more than 20% by mass, the saponification property tends to decrease.
[0051]
The alkaline solution used in the present invention contains a compatibilizing agent. In the present invention, the compatibilizing agent is a hydrophilic compound having a water solubility of 30 g or more with respect to 100 g of the compatibilizing agent at a temperature of 25 ° C. Preferably, the solubility of water is 50 g / 100 g, more preferably 100 g / 100 g. Moreover, when the compatibilizing agent in the present invention is a liquid compound, the boiling point is preferably 100 ° C. or higher, more preferably 120 ° C. or higher.
In the apparatus for an alkaline treatment bath according to the present invention, the compatibilizing agent can prevent the alkaline liquid adhering to the wall surface from being dried, suppress sticking, and stably maintain the solution. In addition, the applied thin film is dried after the alkali solution is applied to the film surface and held for a certain period of time until the saponification stop treatment is performed, so that solids are precipitated, making it difficult to wash out the solids in the water washing process. Deter. Furthermore, phase separation between water as a solvent and an organic solvent is prevented. In particular, the coexistence of the surfactant, the organic solvent, and the compatibilizing agent specified above, the treated film has a reduced haze and is stable and uniform even in the case of a long continuous saponification treatment. A degree of saponification is obtained.
[0052]
As long as the compatibilizing agent used in the present invention is a material satisfying the above conditions, any material can be used as the compatibilizing agent. Preferable compatibilizers include water-soluble polymers containing a repeating unit having a hydroxyl group and / or an amide group including a polyol compound and a saccharide.
As a polyol compound, any of a low molecular compound, an oligomer compound, and a high molecular compound may be sufficient. For example, aliphatic polyols include alkanediols having 2 to 8 carbon atoms (for example, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, glycerin monomethyl ether, glycerin monoethyl ether, cyclohexanediol, cyclohexanedimethanol, Diethylene glycol, dipropylene glycol, etc.), C3-C18 alkanes containing 3 or more hydroxy groups (for example, glycerin, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, diglycerin, Dipentaerythritol, inositol, etc.) and polyalkyleneoxypolyols are formed by bonding the same alkylene diols as described above. Also different alkylene diol which may even be linked to each other but, polyalkylene polyol and more preferably the same alkylene diol mutually bonded. In any case, the number of bonds is preferably 3 to 100. More preferably, it is 3-50. Specific examples include polyethylene glycol, polypropylene glycol, and poly (oxyethylene-oxypropylene).
[0053]
Examples of saccharides include “Natural Polymers” Chapter 2 (Kyoritsu Shuppan Co., Ltd., published in 1984) edited by the Society of Polymer Science, Japan, “Modern Industrial Chemistry 22, Natural Products Industrial Chemistry” II "(Asakura Shoten Co., Ltd., published in 1967) and the like. Saccharides that do not have a free aldehyde group or ketone group and do not exhibit reducibility are preferred. Glucose, sucrose, trehalose-type oligosaccharides in which reducing groups are bonded, glycosides in which reducing groups of saccharides and non-saccharides are combined, and sugar alcohols reduced by hydrogenation of saccharides are all suitable for the present invention. Used. Trehalose type oligosaccharides include saccharose and trehalose. Examples of glycosides include alkyl glycosides, phenol glycosides, mustard oil glycosides, and the like. Examples of the sugar alcohol include D, L-arabit, rebit, xylit, D, L-sorbit, D, L-mannit, D, L-exit, D, L-talit, durisit and allozulcit. Furthermore, a multi-bit obtained by hydrogenation of a disaccharide and a reduced form (reduced water candy) obtained by hydrogenation of an oligosaccharide are also preferably used. Among these, preferred non-reducing sugars for the present invention are sugar alcohol and saccharose. Particularly, D-sorbite, saccharose, and reduced starch syrup are preferable because they have a buffering action in an appropriate pH region and are inexpensive. These non-reducing sugars can be used alone or in combination of two or more.
[0054]
Examples of the water-soluble polymer containing a repeating unit containing a hydroxy group and / or an amide group include natural gums (eg, gum arabic, guar gum, tragand gum, etc.), polyvinyl alcohol, polyvinyl pyrrolidone, dihydroxypropyl acrylate polymer, Examples include addition reactants of celluloses and chitosans with ethylene oxide or propylene oxide and epoxy compounds, alkylene polyols, polyalkyleneoxy polyols, sugar alcohols, and the like.
Among these, alkylene polyols, polyalkyleneoxy polyols, and sugar alcohols are preferable. Specifically, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, di (n-propylene glycol), di (i-propylene glycol), polyethylene glycol (3 to 20 bonds), polypropylene glycol (3 to 10 bonds). ) And glycerin and diglycerin.
[0055]
The content of these compatibilizers is preferably 0.5 to 35% by mass, more preferably 1 to 25% by mass in the alkaline solution.
[0056]
Further, the alkaline solution in the present invention preferably contains an antifoaming agent. This additive can be contained in the alkaline solution at a concentration of preferably 0.001 to 5 mass%, particularly preferably 0.005 to 3 wt%.
Within this range, there is no adhesion of minute bubbles to the film surface, and saponification by the alkali treatment proceeds uniformly without unevenness.
[0057]
Antifoaming agents include oils and fats such as castor oil and linseed oil, fatty acids such as stearic acid and oleic acid, fatty acid esters such as natural wax, alcohols such as polyoxyalkylene monohydric alcohol, di-t- Amylphenoxyethanol, heptylcellosolve, nonylcellosolve, ethers such as 3-heptylcarbitol, phosphate esters such as tributylphosphate and tris (butoxyethyl) phosphate, amines such as diamylamine, polyalkyleneamide, acylate polyamide, etc. Amide series, Aluminum stearate, Calcium stearate, Potassium oleate, Wool oleic acid calcium salt and other metal soap series, Sodium lauryl sulfate ester sulfate series, Dimethylpolysiloxane, Methylphenyl Silicone defoaming agents such as resiloxane, methylhydrogen polysiloxane, fluoropolysiloxane, dimethylpolysiloxane and polyalkylene oxide copolymer, and solution type, emulsion type, paste type silicone oil, etc. Can be mentioned.
[0058]
The alkaline solution used in the present invention preferably further contains an antifungal agent and / or an antibacterial agent. The antifungal agent and antibacterial agent used in the present invention may be anything as long as they do not adversely affect alkali saponification, and specifically, thiazolylbenzimidazole compounds, isothiazolone compounds, chlorophenol compounds , Bromophenol compounds, thiocyanic acid and isothiocyanic acid compounds, acid azide compounds, diazines and triazine compounds, thiourea compounds, alkylguanidine compounds, quaternary ammonium salts, organotin and organozinc compounds, cyclohexylphenol compounds There are various antibacterial and antifungal agents such as imidazole and benzimidazole compounds, sulfamide compounds, active halogen compounds such as chlorinated sodium isocyanurate, chelating agents, sulfites, and antibiotics such as penicillin. . Others E. West, “Water Quality Criteria”, Photo. Sci. and Eng. , Vol9 No. 6 (1965), various antifungal agents described in JP-A-57-8542, 58-105145, 59-126533, 55-111942, and 57-157244, Use of chemicals such as those described in "History of fungi prevention" by Horiguchi Hiroshi, Sankyo Publishing (Sho 57), "Anti-bacteria prevention handbook" Specific examples are shown below, but are not limited thereto.
The addition amount of the above-mentioned antifungal agent and / or antibacterial agent is preferably 0.01 to 50 g / L, more preferably 0.05 to 20 g / L in the alkaline solution.
[0059]
In addition, you may use together another additive for the alkaline solution used for this invention. For example, alkaline liquid stabilizers (antioxidants etc.) etc. are mentioned. In the present invention, the additive of the alkaline solution is not limited to these.
[0060]
The water used for the alkaline solution includes the Japanese Waterworks Act (Act No. 177 of 1957) and the Ministerial Ordinance on Water Quality Standards based on it (August 31, 1978 Ministry of Health and Welfare No. 56), It is preferable to be based on the effects on each element, mineral, etc. in the state of contamination in water specified by the Law No. 125 of July 10, 2011 and its separate table) and the WHO specified tap water standard. Furthermore, in order to ensure the achievement of the effects of the present invention, the calcium concentration is preferably 0.001 to 200 mg / L as the calcium carbonate concentration, and 0.01 to 150 mg / L. Is more preferable, and 0.05 to 10 mg / L is particularly preferable. Within this range, the generation of insoluble matter in the solution is suppressed.
[0061]
The alkaline solution comprising the above composition preferably has a surface tension of 45 mN / m or less (temperature 25 ° C.) and a viscosity in the range of 0.8 to 20 mPa · s (temperature 25 ° C.). . Preferably, the surface tension is 20 to 40 mN / m (temperature 25 ° C.), and the viscosity is 1 to 15 mPa · s (temperature 25 ° C.). Within this range, wettability to the film surface, retention of the solution applied to the film surface, and removal of the alkaline liquid from the film surface after saponification treatment are sufficiently performed.
[0062]
[Alkali saponification method]
The surface treatment method of the cellulose acylate film using the above alkaline solution may be any conventionally known method, and examples thereof include a dipping method, a spraying method, and a coating method.
In particular, when only one surface of the film is uniformly saponified without unevenness, a coating method is preferable. As a coating method, a conventionally known coating method can be used as described later.
The saponification treatment is preferably performed at a treatment temperature in a range not exceeding 120 ° C. at which deformation of the film to be treated, alteration of the treatment liquid, and the like do not occur. Further, the temperature is preferably 10 ° C. or higher and 100 ° C. or lower. In particular, a temperature of 20 to 80 degrees is preferable.
Further, when the coating method is used, the step of saponifying the cellulose acylate film with an alkaline solution at a surface temperature of at least 10 ° C., the step of maintaining the temperature of the cellulose acylate film at least 10 ° C., And it is preferable to implement an alkali saponification process by the process of washing off an alkaline solution from a cellulose acylate film.
The saponification treatment of the cellulose acylate film with an alkaline solution at the surface at a predetermined temperature may include a step of adjusting the temperature to a predetermined temperature before coating, a step of adjusting the alkaline liquid to a predetermined temperature in advance, or The combined process etc. are mentioned. It is preferable to combine with a step of adjusting to a predetermined temperature before application.
[0063]
Preferably, in the step of adjusting the temperature of the cellulose acylate film to 20 degrees or more in advance, collision of a predetermined temperature wind, contact heat transfer using a heat transfer roll, induction heating using a microwave, or radiant heat heating using an infrared heater can be preferably used. Contact heat transfer using a heat transfer roll is particularly preferable in that heat transfer efficiency is high and it can be performed with a small installation area, and that the film temperature rises quickly at the start of conveyance. A general double jacket roll or electromagnetic induction roll (manufactured by Tokuden) can be used.
[0064]
In the step of saponifying the cellulose acylate film with an alkaline solution, it is preferable to suppress the fluctuation of the coating amount to less than 30% with respect to the width direction and the length direction of the film.
Examples of coating methods include die coaters (extrusion coaters, slide coaters), roll coaters (forward roll coaters, reverse roll coaters, gravure coaters), rod (rods wound with thin metal wires) coaters, blade coaters, etc. It can be preferably used. The coating method is described in various documents (for example, Modern Coating and Drying Technology, Edward Cohen and Edgar B. Gutoff, Edits., VCH Publishers, Inc, 1992). It is desirable to suppress the coating amount of the alkaline solution as much as possible in view of waste liquid treatment in order to remove it by washing with water. A rod coater, die coater, gravure coater and blade coater that can be stably operated even with a small coating amount are particularly preferred.
It is also preferable to adopt a continuous coating method.
[0065]
The alkali coating amount required for the saponification reaction is the total number of saponification sites (= theoretical alkali) obtained by multiplying the number of saponification reaction sites per unit area of the cellulose acylate film by the saponification depth necessary to develop adhesion to the alignment film. Application amount) is a guide. As the saponification reaction proceeds, the alkali agent is consumed and the reaction rate decreases, so it is actually preferable to apply several times the theoretical alkali coating amount. Specifically, it is preferably 2 to 20 times the theoretical alkali coating amount, and more preferably 2 to 5 times.
The temperature of the alkaline solution is preferably equal to the reaction temperature (= film temperature).
[0066]
After applying the alkaline solution, the temperature of the cellulose acylate film is kept at least 10 ° C. or more until the saponification reaction is completed. Preferably it is 15 degreeC or more.
The heating means is selected considering that one side of the cellulose acylate film is wet with an alkaline solution. For example, spraying of hot air on the surface opposite to the coated surface, contact heat transfer with a heating roll, induction heating with microwaves, or radiant heat heating with an infrared heater can be preferably used. Infrared heaters are preferred because they can be heated without contact and without air flow, so that the influence on the alkaline solution coating surface can be minimized. As the infrared heater, an electric, gas, oil or steam far infrared ceramic heater can be used. An oil-type or steam-type infrared heater using oil or steam as the heat medium is preferable from the viewpoint of explosion prevention in an atmosphere in which an organic solvent coexists. The temperature of the cellulose acylate film may be the same as or different from the temperature heated before the alkali solution treatment. Further, the temperature may be changed continuously or stepwise during the saponification reaction. For the detection of the film temperature, a commercially available non-contact infrared thermometer can be used, and feedback control may be performed on the heating means in order to control the temperature within the above range.
[0067]
In the present invention, it is particularly preferable to carry out the saponification treatment while conveying the cellulose acylate film. The film conveyance speed is determined by a combination of the composition of the alkaline solution and the coating method. Generally, 10 to 500 m / min is preferable, and 20 to 300 m / min is more preferable. The physical properties (specific gravity, viscosity, surface tension), coating method and coating operation conditions of the alkaline solution are determined so that a stable coating operation can be performed according to the conveyance speed.
[0068]
There are three methods for stopping the saponification reaction between the alkaline solution and the cellulose acylate film. One is to dilute the applied alkaline solution to lower the alkali concentration and lower the reaction rate.The second is to lower the temperature of the cellulose acylate film coated with the alkaline solution to reduce the reaction rate. The third is a method of neutralizing with an acidic liquid.
[0069]
In order to dilute the applied alkaline solution, a method of applying a diluent, a method of spraying the diluent, or a method of immersing the cellulose acylate film together in a container containing the diluent can be employed. Among them, the method of applying a diluting solution and the method of spraying are preferable methods for carrying out the cellulose acylate film continuously. The method of applying the diluent is most preferable because it can be carried out using the minimum amount of diluent.
[0070]
It is desirable that the dilution liquid be applied by a continuous application method in which the dilution liquid can be applied again onto the cellulose acylate film to which the alkaline solution has already been applied. As the coating method, the same contents as those described in the saponification treatment step can be mentioned. In order to reduce the alkali concentration by mixing the alkali solution and the diluting solution quickly, the flow is more laminar than the die coater where the diluting solution is applied (sometimes referred to as coating bead). A roll coater or a rod coater in which the flow is not uniform is preferable.
[0071]
Since the purpose of the diluting solution is to reduce the alkali concentration without dissolving or swelling the cellulose acylate film, the diluting solution must be a solution that dissolves the alkaline agent in the alkaline solution. Therefore, water or a mixed liquid of an organic solvent and water is used as the solvent. The organic solvent may be used alone or in combination of two or more kinds, and can be arbitrarily used as a diluent in a proportion not dissolving or swelling the cellulose acylate film.
[0072]
The application amount of the diluent is determined according to the concentration of the alkaline solution. In the case of a die coater in which the flow in the coating bead is a laminar flow, the coating amount is preferably diluted 1.5 to 10 times the original alkali concentration, more preferably 2 to 5 times. In the case of a roll coater or a rod coater, since the flow in the coating bead is not uniform, mixing of the alkaline solution and the diluting solvent occurs, and the mixed liquid is recoated. Therefore, in this case, since the dilution rate cannot be specified by the application amount of the dilution solvent, the alkali concentration after application of the dilution solvent is measured. Also in the roll coater and the rod coater, the coating amount is preferably diluted 1.5 to 10 times the original alkali concentration, more preferably 2 to 5 times.
[0073]
An acid can also be used to quickly stop the saponification reaction with alkali. In order to neutralize with a small amount, it is preferable to use a strong acid. Furthermore, considering the ease of washing with water, it is preferable to select an acid having a high solubility in water for the salt generated after the alkali and neutralization reaction. Hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, chromic acid and methanesulfonic acid are particularly preferred.
[0074]
In order to neutralize the applied alkaline solution with an acid, a method of applying an acid solution, a method of spraying an acid solution, or a method of immersing the film in a container containing the acid solution can be employed. The method of applying an acid solution and the method of spraying are preferable for carrying out the film while carrying it continuously. The method of applying the acid solution is most preferable because it can be carried out using the minimum necessary acid solution.
[0075]
It is desirable that the acid solution is applied in such a manner that the acid solution can be applied again on the cellulose acylate film on which the alkaline solution has already been applied. The application method is the same as that described in the saponification treatment. In order to quickly mix the alkali solution and the acid solution to neutralize the alkali, a roll coater or a rod coater is preferable.
[0076]
The coating amount of the acid solution is determined according to the type of alkali and the concentration of the alkali solution. In the case of a die coater in which the flow in the coating bead is a laminar flow, the acid coating amount is preferably 0.1 to 5 times, more preferably 0.5 to 2 times the original alkali coating amount. . In the case of a roll coater or a rod coater, since the flow in the coating bead is not uniform, mixing of the alkaline solution and the acid solution occurs, and the mixed solution is recoated. Therefore, in this case, since the neutralization rate cannot be specified by the amount of the acid solution applied, it is necessary to measure the alkali concentration after application of the acid solution. In a roll coater or a rod coater, the coating amount of the acid solution is preferably determined so that the pH after application of the acid solution is 4 to 9, and more preferably determined to be pH 6 to 8.
[0077]
It is also possible to stop the saponification reaction by lowering the temperature of the cellulose acylate film. In order to promote the reaction, the saponification reaction is substantially stopped by sufficiently lowering the temperature from a state maintained at room temperature or higher. The means for lowering the temperature of the film is determined in consideration that one side of the cellulose acylate film is wet. Blowing of cold air to the opposite surface of the coating or contact heat transfer with a cooling roll can be preferably employed. The film temperature after cooling is preferably 0 to 60 ° C, more preferably 5 to 50 ° C, and most preferably 10 to 30 ° C. The film temperature is preferably measured with a non-contact infrared thermometer. From the measured temperature, the cooling temperature can be adjusted by performing feedback control on the cooling means. The temperature lowering means may be used in combination with a method of diluting with the above diluent or a method of neutralizing.
[0078]
The water washing step is performed in order to completely remove the alkaline solution. Further, when a neutralization means is used, it is carried out in order to completely remove compositions such as salts generated by the neutralization. If the composition of the alkaline solution or the salt formed by neutralization remains, not only the saponification reaction proceeds, but also affects the alignment film to be applied later and the formation of the liquid crystalline molecular layer and the alignment of the liquid crystal molecules. .
The washing with water can be carried out by a method of applying water, a method of spraying water, or a method of immersing the polymer film in a container containing water.
[0079]
The water spraying method can be carried out by a method using an application head (for example, a fountain coater or a frog mouth coater) or a method using a spray nozzle used for air humidification, painting, or automatic tank cleaning. The coating method is described in “All about coating” edited by Masayoshi Araki, Research Institute for Processing Technology (1999). Conical or fan-shaped spray nozzles can be arranged in the width direction of the film so that the water flow collides with the entire width. Commercially available spray nozzles (for example, manufactured by Ikeuchi Co., Ltd., manufactured by Spraying Systems) may be used.
[0080]
The higher the water spray speed, the higher the turbulent mixing. However, if the speed is high, the conveyance stability of the cellulose acylate film that is continuously conveyed may be impaired. The spray collision speed is preferably 50 to 1000 cm / second, more preferably 100 to 700 cm / second.
Although it depends on the alkali concentration of the alkaline coating solution used, the secondary additives, and the type of the solvent, it is washed with water to obtain a dilution of at least 100 to 1000 times, preferably 500 to 10,000 times, more preferably 1000 to 100,000 times. Use water.
[0081]
When a certain amount of water is used in the water washing, a batch type washing method in which the whole amount is applied at once rather than being divided into several times is preferable. That is, the amount of water is divided into several parts and supplied to a plurality of washing means installed in tandem in the film transport direction. Appropriate time (distance) is provided between one water washing means and the next water washing means to dilute the alkaline coating liquid by diffusion. More preferably, if the polymer film to be transported is inclined so that the water on the film flows along the film surface, mixed dilution by flow can be obtained in addition to diffusion. As the most preferable method, by providing a draining means for removing the water film on the film between the washing means and the washing means, the washing dilution efficiency can be further increased. Specific examples of draining means include blades used for blade coaters, air knives used for air knife coaters, rods used for rod coaters, and rolls used for roll coaters.
A larger number of washing means arranged in tandem is advantageous. However, from the viewpoint of installation space and equipment cost, usually 2 to 10 stages, preferably 2 to 5 stages are used.
[0082]
The water film thickness after the draining means is preferably thin, but the minimum water film thickness is limited depending on the type of draining means used. In methods such as blades, rods, and rolls that physically contact a solid with a film, even if the solid is an elastic body with low hardness such as rubber, the film surface is scratched or the elastic body is worn away. It is necessary to leave a finite water film as a lubricating fluid. Usually, a water film of several μm or more, preferably 10 μm or more is left as a lubricating fluid.
[0083]
An air knife is preferable as the draining means that can reduce the thickness of the water film to the limit. By setting a sufficient air volume and pressure, the water film thickness can be brought close to zero. However, if the air blowing amount is too large, it may affect the conveyance stability of the cellulose acylate film, such as flapping and deviation, so there is a preferable range. The range is usually 10 to 500 m / sec, preferably 20 to 300 m / sec, more preferably 30 to 200 m / sec, although it depends on the original water film thickness on the cellulose acylate film and the film transport speed. Use wind speed. In order to remove the water film uniformly, the air velocity distribution in the width direction of the cellulose acylate film is usually within 10%, preferably within 5%, and the air supply to the air knife outlet and the air knife is performed. Adjust the method. The narrower the gap between the surface of the cellulose acylate film to be conveyed and the air knife outlet, the better the draining ability, but there is a higher possibility of contact and damage to the cellulose acylate film, so there is an appropriate range. Therefore, the air knife is usually installed with a gap of 10 μm to 10 cm, preferably 100 μm to 5 cm, more preferably 500 μm to 1 cm. Furthermore, by setting up a backup roll on the opposite side of the film to the water-washing surface so as to face the air knife, the setting of the gap can be stabilized and the influence of film flickering, wrinkles, deformation, etc. can be mitigated. Is preferable.
[0084]
It is preferable to use pure water for the washing water. The pure water used in the present invention has a specific electric resistance of at least 1 MΩ or more, in particular, metal ions such as sodium, potassium, magnesium and calcium are less than 1 mg / L, and anions such as chlorine and nitric acid are 0.1 mg / L. Refers to less than. Pure water can be easily obtained by a simple substance such as a reverse osmosis membrane, an ion exchange resin, distillation, or a combination thereof.
[0085]
The higher the washing water temperature, the higher the washing ability. However, in the method in which water is sprayed onto the cellulose acylate film to be conveyed, the area of water in contact with the air is large, and the higher the temperature is, the more the evaporation becomes. Therefore, the surrounding humidity increases and the risk of dew condensation increases. For this reason, the temperature of the washing water is usually set in a range of 5 to 90 ° C, preferably 25 to 80 ° C, more preferably 25 to 60 ° C.
[0086]
If the components of the alkaline coating solution or the product of the saponification reaction are not easily dissolved in water, a solvent washing step for removing water-insoluble components may be added before or after the water washing step. In the solvent washing step, the water washing method, draining means, and the solvent used can be the same as those described in the diluent.
[0087]
A drying process can also be implemented after a water washing process. Usually, the water film can be removed sufficiently with a draining means such as an air knife, so a drying step is not necessary, but before winding the cellulose acylate film into a roll, heat drying to adjust to a preferred moisture content. Also good. Conversely, the humidity can be adjusted with a wind having a set humidity.
[0088]
[Use of saponified cellulose acylate]
The use of the alkali saponified cellulose acylate produced by the method of the present invention will be briefly described.
The optical film of the present invention is particularly useful for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. There is a method in which a cellulose acylate film is treated with an alkali, and a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution is bonded to both surfaces using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed.
[0089]
Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
[0090]
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since the polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, the polarizing plate protective film is particularly preferably used in this portion.
[0091]
The cellulose acylate film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation sheet for liquid crystal display devices. The cellulose acylate film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Charged TNS). Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose acylate film is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device. The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell.
[0092]
The cellulose acylate film of the present invention may be used as a support for an optical compensation sheet of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d ) In the range of 300 to 1500 nm. The optical compensation sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316. The cellulose acylate film of the present invention is particularly advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell.
[0093]
The cellulose acylate film of the present invention is also advantageously used as an optical compensation sheet for TN-type, STN-type, HAN-type, and GH (Guest-Host) type reflective liquid crystal display devices. These display modes have been well known since ancient times. The TN type reflection type liquid crystal display device is described in JP-A-10-123478, WO98848320, and Japanese Patent No. 3022477.
[0094]
The optical compensation sheet used for the reflection type liquid crystal display device is described in WO00-65384. The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell in ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)). The use of these detailed cellulose acylate films described above is described in detail on pages 45 to 59 in the aforementioned technical number 2001-1745.
[0095]
【Example】
[Example 1]
(Preparation of cellulose ester film TF-1)
The composition shown in Table 1 below was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acetate solution A.
[0096]
[Table 1]

[0097]
The composition shown in Table 2 below was charged into a disperser and stirred to dissolve each component to prepare a matting agent solution.
[0098]
[Table 2]

[0099]
The composition shown in Table 3 below was put into a mixing tank and stirred while heating to dissolve each component to prepare a retardation increasing agent solution.
[0100]
[Table 3]

[0101]
[Chemical 1]

[0102]
94.6 parts by mass of the cellulose acetate solution A, 1.3 parts by mass of the matting agent solution, and 4.1 parts by mass of the retardation increasing agent solution were mixed after filtration, and cast using a band casting machine. The mass ratio of the retardation increasing agent to cellulose acetate was 4.6%. The film was peeled off from the band when the residual solvent amount was 30%, and the film having a residual solvent amount of 13% by mass was stretched laterally at a stretch ratio of 28% using a tenter under the condition of 130 ° C. Hold at 30 ° C. for 30 seconds. Thereafter, the clip was removed and dried at 140 ° C. for 40 minutes to produce a cellulose acetate film. The film thickness of the finished cellulose acetate film was 80 μm.
[0103]
(Preparation of saponification film SF-1)
The cellulose acetate film having a roll width of 1000 mm is passed through a dielectric heating roll having a temperature of 60 ° C. and heated to a film surface temperature of 40 ° C., and then an alkali solution (S-1) having the composition shown in Table 4 below is applied to a rod coater. Application amount 13.5cc / m²After coating for 15 seconds under a steam far-infrared heater manufactured by Noritake Co., Ltd., heated to 110 ° C., 3 cc / m of pure water was also used using a rod coater.²Applied. The film temperature at this time was 40 ° C. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then the saponification film SF-1 was produced by staying in a drying zone at 70 ° C. for 5 seconds and drying.
Cellulose acetate film 2000m using 35L of alkaline solution (S-1)²Was saponified.
[0104]
[Table 4]

[0105]
The viscosity of the alkaline solution (S-1) was 5.5 mPa · s (temperature: 25 ° C.), and the surface tension was 22.5 mN / m (25 ° C.).
[0106]
(Preparation of comparative saponification film SFR-1)
The comparative treatment liquid (SR-1) having the same composition as the alkaline solution (S-1) except that 1.0% by mass of the surfactant (K-1) was removed from the composition of the alkaline solution (S-1). A comparative saponified film SFR-1 was produced using this treatment solution in the same manner as the saponified film SF-1. The viscosity of the alkaline solution (SR-1) was 5.5 mPa · s (temperature: 25 ° C.), and the surface tension was 22.6 mN / m (25 ° C.).
[0107]
(Preparation of comparative saponification film SFR-2)
A comparative treatment liquid (SR-2) having the composition shown in Table 5 below was prepared by removing the compatibilizing agent from the composition of the alkaline solution (S-1) and adding that amount proportionally to water and the organic solvent. A saponified film SFR-2 for comparison was produced by the same method as that for producing the saponified film SF-1 using this treatment liquid. The viscosity of the alkaline solution (SR-2) was 3.5 mPa · s (temperature 25 ° C.), and the surface tension was 22.0 mN / m (25 ° C.).
[0108]
[Table 5]

[0109]
Table 6 below shows the properties of the alkali solutions (S-1, SR-1 and SR-2) used and the performances of the saponified films (SF-1, SFR-1 and SFR-2) produced. A and B in the table are samples immediately after the start of the saponification treatment, A, 2000 m²The sample after the treatment is represented as B, and each is observed and evaluated and shown in the table.
[0110]
[Table 6]

[0111]
The evaluation methods in which the evaluation items described in Table 6 are assigned the note numbers 1) to 4) are as follows.
1) Properties of alkaline solution
The transparency of the alkaline solution was visually evaluated using the following criteria.
◯: No turbidity or precipitation is observed, completely transparent
×: Turbidity occurs
XX: Precipitation occurs
[0112]
2) Contact angle with water
Using a contact angle meter (CA-X contact angle meter, manufactured by Kyowa Interface Science Co., Ltd.), a droplet having a diameter of 1.0 mm using pure water as a liquid in a dry state (20 ° C./65% RH) Was made on the needle tip and brought into contact with the surface of the film to form droplets. The angle formed by the solid surface and the tangent to the liquid surface at the point where the solid liquid is in contact was defined as the contact angle.
About each film, the contact angle of 9 places of both ends and the center was measured in the surface of 1 square meter, and the upper limit and the lower limit were described. However, the range of ± 1 degree is the range of variation in measurement, and is indicated by the median value.
[0113]
3) Haze
The haze of the saponified film was measured using a NHD101DP type optical tester manufactured by Nippon Denshoku Co., Ltd.
4) Foreign matter, cloudiness
A saponified film was cut out to a length of 1 m in the longitudinal direction with the full width, and the sample was observed visually and with a loupe for light and foreign matter and turbidity while allowing light to pass through on the Saucusten and evaluated using the following criteria.
◯: No foreign matter or turbidity is observed at all (evaluated by 10 people, a level that no one can recognize)
Δ: Foreign matter and turbidity are weakly generated (level evaluated by 10 people and recognized by 2 to 5 people)
X: Foreign matter and turbidity are strongly generated (level evaluated by 10 people and recognized by 6 or more people)
[0114]
As shown in Table 6, in the embodiment of the present invention, 2000 m²Even after the film was treated, the alkaline solution was transparent, and the film surface after the saponification treatment had a contact angle with water of 30 degrees. Moreover, the haze of the saponified film was small, and no foreign matter or turbidity was observed.
On the other hand, the comparative dissolved alkali solutions (SR-1) and (SR-2) are 2000 m.²Turbidity or precipitation occurred after treatment.
In addition, the comparatively soluble alkali saponified films SFR-1 and SFR-2 had almost the same performance as the film SF-1 of the present invention immediately after the start of the saponification process (SFR-1A and SFR-2A). , 2000m²In the samples at the time of processing (SFR-1B and SFR-2B), both of the contact angle with water increased in the plane, the haze value increased, and turbidity and generation of foreign matter were observed on the film surface. It was not a level that was put to practical use.
[0115]
Next, using the film SF-1 of the present invention in which good performance was obtained in both the A part and B part samples in the saponification treatment, an optical film was prepared as described below, and performance evaluation was performed.
[0116]
(Formation of alignment film)
Sample immediately after the start of saponification treatment of the film SF-1 (SF-1A) and 2000 m²An alignment film coating solution comprising 20 parts by mass of modified polyvinyl alcohol having the following structure, 360 parts by mass of water, 120 parts by mass of methanol, and 0.5 parts by mass of glutaraldehyde is applied to the saponified surface of the sample (SF-1B) at the time of treatment. 30cc / m with a rod coater²The alignment film was formed by applying and rubbing using a velvet cloth rubbing roll placed vertically in the conveying direction after being applied and dried with hot air of 60 ° C. for 60 seconds and further with hot air of 90 ° C. for 150 seconds.
Modified polyvinyl alcohol
[0117]
[Chemical 2]

[0118]
(Formation of optically anisotropic layer)
On the alignment films formed on the samples SF-1A and SF-1B, 41.01 parts by mass of the following discotic compound, ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 1 .22 parts by mass, polyfunctional acrylate monomer (NK ester A-TMMT, Shin-Nakamura Chemical Co., Ltd.) 2.84 parts by mass, cellulose acetate butyrate (CAB551-0.2, Eastman Chemical Co., Ltd.) 0.90 parts by mass, Cellulose acetate butyrate (CAB531-1, Eastman Chemical Co.) 0.23 parts by mass, photopolymerization initiator (Irgacure 907, Ciba Geigy Co.) 1.35 parts by mass, sensitizer (Kayacure DETX, Nippon Kayaku) After dissolving 0.45 parts by mass in 102 parts by mass of methyl ethyl ketone Was applied with a # 4 wire bar. Then, it heated for 2 minutes in the hot air zone of 130 degreeC to connect, and the discotic compound was orientated. Finally, under an atmosphere of 80 ° C., with a film surface temperature of about 100 ° C., using a 120 W / cm high-pressure mercury lamp, UV irradiation is performed for 0.4 seconds to polymerize the discotic compound. Formed. The Re retardation value of the optically anisotropic layer measured at a wavelength of 633 nm was 45 nm. The angle (tilt angle) between the disk surface and the first transparent support surface was 39 degrees on average.
[0119]
[Chemical 3]

[0120]
(Evaluation method of optical compensation sheet)
Haze
About obtained films SF-1 to SF-4 and SFR-1, NHD manufactured by Nippon Denshoku Co., Ltd.? Haze was measured using a 101DP type optical testing machine.
Transmitted light unevenness
Each optical compensation sheet was sandwiched between two polarizing plates arranged in crossed Nichols, and the unevenness of transmitted light was visually observed for sensory evaluation.
○: Not generated at all (level that 10 people evaluate and one cannot recognize)
Δ: Weak occurrence (level evaluated by 10 people and recognized by 1 to 5 people)
X: Strongly generated (level evaluated by 10 people and recognized by 6 or more people)
Adhesion
Each optical compensation sheet was cut into 30 cm × 25 cm and left for 1 day under conditions of 25 ° C. and 60% relative humidity, and then the cellophane tape having a width of 1.2 cm and a length of 10 cm on the optically anisotropic layer side (No. .405) were affixed to each other for 1 second, and peeled between the film and the alignment film was inspected. Relative adhesion superiority or inferiority was evaluated according to how many of the 10 cellophane tapes were broken between coating layers.
Table 7 shows the evaluation results.
[0121]
[Table 7]

[0122]
As shown in Table 7, both SF-1A and SF-1B subjected to the saponification treatment according to the present invention were good with low haze and no unevenness in transmitted light. Also, the adhesion was sufficient and good.
As described above, the saponified cellulose acylate prepared by the method of the present invention and the optical film using the same show performance with excellent uniformity and good adhesion.
[0123]
[Example 2]
(Saponified cellulose triacetate film)
Cellulose triacetate film: Fujitac TD80UF (Fuji Photo Film Co., Ltd.) was hit with 100 ° C hot air, heated to 45 ° C, and then heated to 25 ° C with the following alkaline solution (S-2) with a rod coater. Use 14cc / m²After 13 seconds, apply pure water at 5cc / m again using a rod coater.²Applied. The film temperature at this time was 45 ° C. Next, 1000cc / m using an extrusion type coater²The pure water was applied, washed with water, and after a lapse of 5 seconds, 100 m / s of air was collided with the water application surface from the air knife. Washing with an extrusion coater and draining with an air knife were repeated twice, and then retained in a drying zone at 80 ° C. for 10 seconds and dried to prepare a saponified film SF-2. As in Example 1, 2000 m²The film was saponified.
[0124]
[Table 8]

[0125]
The viscosity of the alkaline solution (S-2) was 5.6 mPa · s (temperature 25 ° C.), and the surface tension was 22.8 N / m (25 ° C.).
[0126]
At the start of saponification treatment of the obtained film and 2000 m²It was 60 mN / m as a result of calculating | requiring the surface energy of each film sample (SF-2A and SF-2B) at the time of processing by the following method.
The surface energy was determined by the contact angle method described in “Wetting Fundamentals and Applications” (issued by Realize 1989.12.10). Two solutions of water and methylene iodide with known surface energy are dropped on the cellulose acetate film, and at the intersection of the surface of the droplet and the surface of the film, the angle formed by the tangent drawn to the droplet and the film surface The angle containing the droplet was defined as the contact angle, and the surface energy of the film was calculated by calculation.
[0127]
(Polarizer)
A polarizing film is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol-based adhesive, the optical compensation sheet prepared in Example 1 is placed on one side of the polarizing film and the saponification film on the other side. SF-2A was affixed with a polyvinyl alcohol adhesive and then dried at 80 ° C. for 10 minutes. The transmission axis of the polarizing film and the slow axis of the optical compensation sheet prepared in Example 1 were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the cellulose triacetate film were arranged so as to be orthogonal. In this way, a polarizing plate was produced.
Further, a polarizing plate was produced in the same manner as described above using SF-2B instead of the saponification film SF-2A.
[0128]
(Liquid crystal display device)
A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell was peeled off, and each polarizing plate prepared above was prepared in Example 1 instead. The optical compensation sheets were attached to the viewer side and the backlight side one by one through an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side were arranged to be in the O mode.
[0129]
About the liquid crystal display device produced in this way, the drawing unevenness at the time of black display (L1) was visually observed using a measuring machine (EZ-Contrast 160D, manufactured by ELDIM).
As a result, when the saponification film SF-2A or SF-2B according to the method of the present invention was installed as a protective film, a clear and high-brightness image with no fogging was obtained on the entire screen. .
From the above visual observation results, it was shown that those using a cellulose acylate film obtained by saponifying a long film by the method of the present invention have good optical properties.
[0130]
Example 3
A cellulose acylate film provided with an antireflection film was produced according to the description in Example 1 of JP-A No. 2002-182033. Next, a polyethylene terephthalate film (SAT-106TS, manufactured by Sanei Kaken Co., Ltd.) was bonded to the surface of the antifouling layer of the cellulose acylate film. Using this film as an immersion processing apparatus, a master etching processor for electronic plate making system: E-380 ° C., an alkaline solution (S-3) having the following composition was placed in this apparatus and the liquid temperature was set to 45 ° C. After immersing the film so that the immersion time was 10 seconds, the film was immersed in water to sufficiently wash away the alkaline solution. Subsequently, after being immersed in a 0.5% dilute sulfuric acid aqueous solution for 10 seconds, it was immersed in water and thoroughly washed. Furthermore, this film was dried at 100 ° C. to prepare a saponified cellulose acylate film (SF-3). The polyethylene terephthalate film was removed from the cellulose triacetate film to produce a first polarizing plate protective film.
[0131]
[Table 9]

[0132]
The viscosity of the alkaline solution (S-3) was 2.0 mPa · s (temperature 25 ° C.), and the surface tension was 35.0 mN / m (25 ° C.).
[0133]
(Preparation of second polarizing plate protective film)
Polyethylene terephthalate film (SAT-106TS, manufactured by Sanei Kaken Co., Ltd.) was bonded to one surface of another cellulose triacetate film produced by the above method. Similarly to the production of the first polarizing plate protective film, after the saponification treatment, the polyethylene terephthalate film was removed to produce a second polarizing plate protective film.
[0134]
(Preparation of polarizing plate)
A 75 μm-thick polyvinyl alcohol film (manufactured by Kuraray Co., Ltd.) was immersed in an aqueous solution in which 7 parts by mass of iodine and 105 parts by mass of potassium iodide were dissolved in 1000 parts by mass of water to adsorb iodine to the film. Next, the film was stretched uniaxially in the longitudinal direction 4.4 times in a 4% by mass boric acid aqueous solution at 40 ° C., and then dried in a tension state to produce a polarizing film. A polyvinyl alcohol-based adhesive is used as an adhesive, and the surface of the saponified cellulose triacetate film of the first polarizing plate protective film is bonded to one surface of the polarizing film, and the other surface of the polarizing film is bonded to the first surface. 2 The surfaces of the saponified cellulose triacetate film of the polarizing plate protective film were bonded together. In this way, a polarizing plate was produced.
[0135]
(Evaluation of polarizing plate)
100 polarizing plates were prepared by the above method, and each was bonded to a glass plate using an acrylic adhesive, and they were put in a thermostatic chamber. The inside of the thermostatic chamber was 70 ° C. and an atmosphere of 93% RH. A durability test was conducted for a total of 1000 hours while alternately changing the setting to 25 ° C. and 93% RH atmosphere every 12 hours. When 100 samples taken out from the thermo-hygrostat were examined for peeling between the polarizing plate and the glass plate and generation of bubbles, no peeling or generation of bubbles was observed in all 100 samples.
Further, the polarizing plates on both sides of a commercially available thin-film transistor (TFT) type liquid crystal monitor were peeled off, and the polarizing plates were attached to both sides, and the presence or absence of black display and white display unevenness was visually determined. No visual defects such as unevenness were found on the entire screen.
[0136]
Example 4
(Saponified cellulose triacetate film)
The antireflection film described in Example 3 was attached to one side of the cellulose acylate film, hot air of 80 ° C. was collided with the surface on which the antireflection film was not applied, heated to 45 ° C., and then 35 ° C. A coating amount of 5 cc / m for each alkali solution (S4-7) having the composition shown in Table 10 below, which was kept warm, using a rod coater²so After 10 seconds, apply pure water again at 5cc / m using a rod coater.²Applied. The film temperature at this time was 45 ° C. Next, 1000cc / m using an extrusion type coater²After washing for 5 seconds, 100 m / s of wind was blown from the air knife. Washing with an extrusion coater and draining with an air knife were repeated twice, and then the saponification films SF-4 to SF-7 were prepared by staying in a drying zone at 80 ° C. for 10 seconds and drying.
[0137]
[Table 10]

[0138]
The solubility parameters of organic solvents in Tables 4, 5, 8, and 9 and Table 10 above ([mJ / m³]^1/2) And I / O values are mentioned above in the specification but are listed below.

The viscosity of each alkaline solution (S-4 to S-7) was 1.8 to 6 mPa · s (temperature 25 ° C.), and the surface tension was 20 to 30 mN / m (25 ° C.).
[0139]
The contact angle with water of each film (SF-4 to 7) was in the range of 30 to 35 degrees.
Next, instead of the saponified film used in Example 3, saponified films SF-4 to SF-7 were used to produce polarizing plates. As a result of evaluating the performance of the polarizing plate in the same manner as in Example 3, the performance equivalent to that of the sample of Example 3 was shown.
[0140]
【The invention's effect】
According to the alkali saponification method of the cellulose acylate film of the present invention using an alkali solution containing an alkali agent, water, an organic solvent, a compatibilizing agent and a surfactant, the film surface is free from defects such as haze. Can be saponified with high uniformity and with high productivity. This alkali saponified film can be easily incorporated into an optical compensation sheet for a large area liquid crystal display device free from display defects. In addition, a cell source acylate film for a transparent support having excellent adhesion between the transparent support of the optical compensation sheet and the alignment film can be obtained.

Claims (9)

A method for alkaline saponification of a cellulose acylate film, comprising subjecting a cellulose acylate film to alkaline saponification using an alkaline solution containing at least an alkaline agent, water, an organic solvent, a surfactant and a compatibilizing agent. The organic solvent has an inorganic / organic value (I / O value) of 0.5 or more and a solubility parameter of 16 to 40 [mJ / m ³ ] ^1/2. The alkali saponification method of the cellulose acylate film described in 1. The cellulose acylate film according to claim 1 or 2, wherein the surfactant is at least one selected from a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. Alkaline saponification method. The compatibilizer is at least one selected from polyol compounds having a water solubility of 30 g or more with respect to 100 g of the compatibilizer at a temperature of 25 ° C. The alkali saponification method of the cellulose acylate film of description. The alkali solution has an alkali agent concentration of 0.1 to 5 mol / Kg, a surface tension of 45 mN / m or less, and a viscosity of 0.8 to 20 mPa · s. An alkali saponification method for a cellulose acylate film according to claim 1. The method for alkali saponification of a cellulose acylate film according to any one of claims 1 to 5, wherein the alkaline solution contains an antifoaming agent. The cellulose acylate according to any one of claims 1 to 6, comprising a step of applying the alkaline solution to the cellulose acylate film at room temperature or higher and a step of washing the alkaline solution from the cellulose acylate film. Method for alkali saponification of rate film. A surface saponified cellulose acylate film obtained by the alkali saponification method according to claim 1. An optical film comprising the surface saponified cellulose acylate film according to claim 8.